Primes:
#include<iostream> #include<cmath> using namespace std; #define N 500 int a[N]; int judge(int n){ if(n==1||n==2) return 1; int i; int t=0; for(i=2;i<=sqrt(n);++i){ if(n%i==0){ t=1; break; } } if(t==1) return 1; else return 0; } int main(){ int n; int i=0; while(cin>>n){ if(n<=0) break; a[i++]=n; } int j; for(j=0;j<i;++j){ if(judge(a[j])==1) cout<<j+1<<": no"<<endl; else cout<<j+1<<": yes"<<endl; } return 0; }