Compilare: user.cpp: In function ‘int main()’: user.cpp:28:10: warning: statement has no effect [-Wunused-value] for(i; i <= n ; ++i) ^ user.cpp:43:10: warning: statement has no effect [-Wunused-value] for(i; i <= n ; ++i) ^ user.cpp:7:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("magic2.in", "r", stdin); ^ user.cpp:8:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("magic2.out", "w", stdout); ^ user.cpp:9:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:12:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x[i][j]); ^