Compilare: user.c: In function ‘read’: user.c:25:13: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(FIN, "r", stdin); ^ user.c:27:11: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d", &N, &A, &B, &C); ^ user.c: In function ‘write’: user.c:65:13: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(FOUT, "w", stdout); ^