Compilare: user.cpp: In function ‘int main()’: user.cpp:103:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < sol.size(); ++i) ^ user.cpp:92:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("expr.in", "r", stdin); ^ user.cpp:93:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("expr.out", "w", stdout); ^ user.cpp:95:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s", sir); ^