Compilare: user.cpp: In function ‘int main()’: user.cpp:11:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("photo.in", "r", stdin); ^ user.cpp:12:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("photo.out", "w", stdout); ^ user.cpp:14:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d", &N, &A); ^ user.cpp:16:68: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d", &a[i].first, &a[i].second), ap[a[i].second] = 1; ^