Compilare: main.cpp: In function 'int main()': main.cpp:98:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0 ; i < ans.size() - 1 ; i++) ~~^~~~~~~~~~~~~~~~ main.cpp:51:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] FastIO , FILES; ^ main.cpp:51:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]