Compilare: main.cpp:1:2: warning: #import is a deprecated GCC extension [-Wdeprecated] #import<cstdio> ^~~~~~ main.cpp:2:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type] main(){freopen("sah.in","r",stdin);freopen("sah.out","w",stdout);int n,i,j;scanf("%d",&n);for(i=0;i<n;++i){for(j=0;j<n;++j)printf("%d ",((i>>1)<<1)^(j<(i>>1)?0:1));printf("\n");}} ^ main.cpp: In function 'int main()': main.cpp:2:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] main(){freopen("sah.in","r",stdin);freopen("sah.out","w",stdout);int n,i,j;scanf("%d",&n);for(i=0;i<n;++i){for(j=0;j<n;++j)printf("%d ",((i>>1)<<1)^(j<(i>>1)?0:1));printf("\n");}} ^ main.cpp:2:65: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] main(){freopen("sah.in","r",stdin);freopen("sah.out","w",stdout);int n,i,j;scanf("%d",&n);for(i=0;i<n;++i){for(j=0;j<n;++j)printf("%d ",((i>>1)<<1)^(j<(i>>1)?0:1));printf("\n");}} ^ main.cpp:2:90: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] main(){freopen("sah.in","r",stdin);freopen("sah.out","w",stdout);int n,i,j;scanf("%d",&n);for(i=0;i<n;++i){for(j=0;j<n;++j)printf("%d ",((i>>1)<<1)^(j<(i>>1)?0:1));printf("\n");}} ^