Compilare: main.cpp: In function 'int main()': main.cpp:53:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < ans.size() - 1; ++i) ~~^~~~~~~~~~~~~~~~ main.cpp:34:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen(input, "r", stdin); ^ main.cpp:35:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen(output, "w", stdout); ^