diff --git a/main.cpp b/main.cpp
index 74b7699..01aaa58 100644
--- a/main.cpp
+++ b/main.cpp
@@ -16,6 +16,7 @@ typedef uint16_t Storage;
 const size_t ARGS_COUNT = 4;
 const size_t FUNCTION_LEN = 1ll << ARGS_COUNT;
 const size_t FUNCTIONS_COUNT = 1ll << FUNCTION_LEN;
+const bool ONLY_CREATE_CLASSES = true;
 typedef Function<Storage, FUNCTION_LEN> MyFunction;
 typedef BoolSquareMatrix<Storage, ARGS_COUNT> MyMatrix;
 
@@ -242,6 +243,51 @@ string preprocess_monom(string monom) {
     return monom;
 }
 
+inline bool exists_test0 (const std::string& name) {
+    ifstream f(name.c_str());
+    return f.good();
+}
+
+
+string get_out_file_name(size_t rank_ind) {
+    return string("base_" + to_string(ARGS_COUNT) + "_rank_" + to_string(rank_ind) + ".txt");
+}
+
+size_t recover_ranks(vector< vector<MyFunction> >& ranks, vector<int8_t>& used_map, size_t& functions_remains) {
+    for (size_t rank_ind = 2; true; ++rank_ind) {
+        ifstream f_in(get_out_file_name(rank_ind).c_str(), std::ios::binary);
+        if ( not f_in.good() )
+            return rank_ind;
+        ranks.push_back(vector<MyFunction>());
+        while ( not f_in.eof() and f_in.good() ) {
+            char buf[sizeof(Storage)];
+            f_in.read(buf, sizeof(Storage));
+            Storage function_value = *reinterpret_cast<Storage*>(buf);
+            MyFunction f(function_value);
+            if (used_map.at(f.value()))
+                continue;
+            used_map.at(f.value()) = rank_ind;
+            --functions_remains;
+            ranks.back().push_back(f);
+        }
+    }
+}
+
+void save_rank(size_t rank_ind, vector<MyFunction>& rank_items) {
+    ofstream f_out(get_out_file_name(rank_ind).c_str(), ios::binary);
+    for (auto f: rank_items) {
+        Storage function_value = f.value();
+        f_out.write(reinterpret_cast<char*>(&function_value), sizeof(function_value));
+    }
+}
+
+
+void clean_trash_ranks(vector< vector<MyFunction> >& ranks) {
+    for (size_t rank_ind = 2; rank_ind < ranks.size() - 1; ++rank_ind)
+        ranks.at(rank_ind).clear();
+}
+
+
 void fill_ranks(vector<MyFunction> monomials) {
     vector<int8_t> used_map(FUNCTIONS_COUNT, 0);
     size_t functions_remains = FUNCTIONS_COUNT;
@@ -255,30 +301,61 @@ void fill_ranks(vector<MyFunction> monomials) {
         --functions_remains;
         used_map.at(el.value()) = 1;
     }
-    size_t total_ranks = 1;
-    for (total_ranks = 1; functions_remains; ++total_ranks) {
-        ranks.push_back(vector<MyFunction>());
+    size_t total_ranks = recover_ranks(ranks, used_map, functions_remains);
+    clean_trash_ranks(ranks);
+    cout << "recovered to " << total_ranks << endl;
+    cout << "current ranks: " << endl;
+    for (auto&& r: ranks)
+        cout << r.size() << " ";
+    cout << endl;
+    for (; functions_remains; ++total_ranks) {
         cout << "rank index = " << total_ranks << " remains: " << functions_remains << endl;
-        for (auto el_first: ranks.at(total_ranks - 1)) {
-            for (auto el_second: ranks.at(1)) {
+        vector<int8_t> temp_used_map(FUNCTIONS_COUNT, 0);
+        for (size_t ind_first = 0; ind_first != ranks[1].size(); ++ind_first) {
+            if ( ind_first % 20 == 0 ) {
+                for (auto&& r: ranks)
+                    cout << r.size() << " ";
+                cout << endl;
+                cout << 100. * ind_first / ranks[1].size() << "% for " << ranks[1].size()
+                    << " x " << ranks.back().size() << endl;
+            }
+            const auto el_first = ranks[1][ind_first];
+            for (auto el_second: ranks.back()) {
                 MyFunction res_el = el_first xor el_second;
-                if ( used_map[res_el.value()] == 0 ) {
-                    --functions_remains;
-
-                    function_formulas[res_el.value()] =
-                        preprocess_monom(function_formulas[el_first.value()]) +
-                        " + " + preprocess_monom(function_formulas[el_second.value()]);
-
-                    used_map.at(res_el.value()) = total_ranks;
-                    ranks.at(total_ranks).push_back(res_el);
+                if constexpr ( not ONLY_CREATE_CLASSES ) {
+                    if ( used_map[res_el.value()] == 0 ) {
+                        function_formulas[res_el.value()] =
+                            preprocess_monom(function_formulas[el_first.value()]) +
+                            " + " + preprocess_monom(function_formulas[el_second.value()]);
+                    }
                 }
+                temp_used_map[res_el.value()] = total_ranks;
             }
         }
-        if ( total_ranks - 1 > 1 )
-            ranks.at(total_ranks - 1).clear();  // больше не нужен
+
+        ranks.push_back(vector<MyFunction>());
+        clean_trash_ranks(ranks);
+        for (size_t func_ind = 0; func_ind < temp_used_map.size(); ++func_ind) {
+            if (not temp_used_map[func_ind] or used_map[func_ind] != 0)
+                continue;
+            --functions_remains;
+            auto cur_fn = MyFunction(func_ind);
+            auto val = cur_fn.value();
+            if (val >= used_map.size()) {
+                cout << val << " " << cur_fn.string() << endl;
+                continue;
+            }
+            used_map[val] = total_ranks;
+            ranks.back().push_back(cur_fn);
+        }
+        save_rank(total_ranks, ranks.back());
         cout << "size for rank " << total_ranks << " is " << ranks.at(total_ranks).size() << endl;
     }
 
+    if constexpr ( ONLY_CREATE_CLASSES ) {
+        return;
+    }
+
     auto possible_tranformations = get_good_matrices();
     cout << "Total " << possible_tranformations.size() << " linear tranformations" << endl;