Compilare: user.cpp: In function ‘int main()’: user.cpp:72:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (k = 0; k < val.size(); k++) ^ user.cpp:21:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("logic.in","r",stdin); ^ user.cpp:22:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("logic.out","w",stdout); ^ user.cpp:24:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &N); ^ user.cpp:35:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(S); p = &S[0]; ^ user.cpp:43:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(T); p = &T[0]; ^ /tmp/ccoymZEV.o: In function `main': user.cpp:(.text.startup+0x156): warning: the `gets' function is dangerous and should not be used.