Compilare: user.cpp: In function ‘int main()’: user.cpp:16:11: warning: unused variable ‘i’ [-Wunused-variable] int m,n,k,i,j; ^ user.cpp:31:5: warning: unused variable ‘r’ [-Wunused-variable] int r=1; ^ user.cpp:14:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("castel.in","r",stdin); ^ user.cpp:15:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("castel.out","w",stdout); ^ user.cpp:17:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d",&m,&n,&k); ^ user.cpp:20:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&a[i][j]); ^