Compilare: user.cpp: In function ‘int main()’: user.cpp:4:20: warning: unused variable ‘i’ [-Wunused-variable] int main(){int n,m,i;freopen("dmin2.in","r",stdin);freopen("dmin2.out","w",stdout);scanf("%d%d",&n,&m);printf("%lld",1LL*(n-2)*(n-3)/2-m+n-2); return 0;} ^ user.cpp:4:51: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] int main(){int n,m,i;freopen("dmin2.in","r",stdin);freopen("dmin2.out","w",stdout);scanf("%d%d",&n,&m);printf("%lld",1LL*(n-2)*(n-3)/2-m+n-2); return 0;} ^ user.cpp:4:83: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] int main(){int n,m,i;freopen("dmin2.in","r",stdin);freopen("dmin2.out","w",stdout);scanf("%d%d",&n,&m);printf("%lld",1LL*(n-2)*(n-3)/2-m+n-2); return 0;} ^ user.cpp:4:103: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] int main(){int n,m,i;freopen("dmin2.in","r",stdin);freopen("dmin2.out","w",stdout);scanf("%d%d",&n,&m);printf("%lld",1LL*(n-2)*(n-3)/2-m+n-2); return 0;} ^