水。
#include <cstdio>
#include <cmath>
bool f(int n){
int t = (int)sqrt(n);
for(int i = 2; i <= t; ++i)
if(n % i == 0) return 0;
return 1;
}
int main(){
int a[30] = {0, 3, 7}, i;
for(i = 3; i != 30; ++i)
a[i] = a[i - 1] + a[i - 2];
while(scanf("%d", &i), i != -1)
printf(f(a[i]) == 0 ? "No\n" : "Yes\n");
return 0;
}原文：http://blog.csdn.net/chang_mu/article/details/19704633