Compilare: main.cpp: In function 'int main()': main.cpp:30:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < elem.size(); i++) ~~^~~~~~~~~~~~~ main.cpp:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < elem.size(); i++) ~~^~~~~~~~~~~~~ main.cpp:22:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("urat.in", "r", stdin); ^ main.cpp:23:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("urat.out", "w", stdout); ^