Compilare: user.cpp: In function ‘int main()’: user.cpp:52:18: warning: statement has no effect [-Wunused-value] X==1; ^ user.cpp:68:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v.size();i++) ^ user.cpp:21:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.in", "r", stdin); ^ user.cpp:22:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.out", "w", stdout); ^ user.cpp:26:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i", &n); ^ user.cpp:30:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i %i", &a, &b); ^