Compilare: main.cpp: In function 'int32_t main()': main.cpp:18:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1 ; i <= str.size() - 2 ; ++ i) ~~^~~~~~~~~~~~~~~~~ main.cpp:11:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("chei.in", "r", stdin) ; ^ main.cpp:12:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("chei.out", "w", stdout) ; ^