Compilare: main.cpp: In function 'int add_cell(std::pair<int, int>, std::vector<std::vector<int> >&, std::vector<std::vector<int> >&)': main.cpp:12:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 12 | for (int i = 0; i < m1.size(); i++) | ~~^~~~~~~~~~~ main.cpp: In function 'void multiply_matrix(std::vector<std::vector<int> >&, std::vector<std::vector<int> >&)': main.cpp:19:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 19 | for (int i = 0; i < matrix1.size(); i++) | ~~^~~~~~~~~~~~~~~~ main.cpp:20:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 20 | for (int j = 0; j < matrix2.size(); j++) | ~~^~~~~~~~~~~~~~~~ main.cpp:23:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 23 | for (int l = 0; l < matrix1.size(); l++) | ~~^~~~~~~~~~~~~~~~ main.cpp: In function 'void show(std::vector<std::vector<int> >&)': main.cpp:31:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 31 | for (int i = 0; i < m.size(); i++) | ~~^~~~~~~~~~ main.cpp:33:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 33 | for (int j = 0; j < m[i].size(); j++) | ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:76:27: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses] 76 | if (reach & 1 == 1) | ~~^~~~