Compilare: user.cpp: In function ‘void custi(std::vector<std::vector<int> >, std::vector<int>&)’: user.cpp:20:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int size = 0; size < M.size() - 1; ++size) { ^ user.cpp: In function ‘int main()’: user.cpp:35:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sume.in", "r", stdin); ^ user.cpp:36:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sume.out", "w", stdout); ^