g.c

The 5th Annual Shantou Univ.Collegiage Programming Contest

#include <stdio.h>

int chknum(int n)
{
    int i=2;
    while(1)
    {
        if(n<i) break;
        if(n%i==0)
        {
            n/=i;
            i++;
        }
        else
        {
            n--;
            if(n%i==0)
            {
                n/=i;
                i++;
            }
            else break;
        }
    }
    if(n==1) return 1;
    else return 0;
}

int main()
{
    int n;
    while(1)
    {
        scanf("%d",&n);
        if(n==-1) break;
        if(chknum(n)) printf("YES\n");
        else
        {
            if(chknum(n-1)) printf("YES\n");
            else printf("NO\n");
        }
    }
    return 0;
}