好惨啊！弄了我这么久...
还好最后AC了
#include<cstdio>
int n;
int tot=0;
int ans[25000];

int main()
{
    long long t0,t1=1,t2=1;
    for (int i=3;tot<22000;i++)
    {
        t0=t1+t2;
        t2=t1;
        t1=t0;
        if (t0>=1e18)
        {
           t0/=10;
           t1/=10;
           t2/=10;
        }
        bool p=true;
        for (int j=2;j*j<=i;j++)
            if (i%j==0)
            {
               p=false;
               break;
            }
        if (p || i==4)
        {
           long long p=t0;
           while (p>=1e9) p/=10;
           ans[++tot]=p;
        }
    }
    while (scanf("%d",&n)==1) printf("%d\n",ans[n]);
    return 0;
}