（寒假CF）乐

题意：ekjfkj=output 依此解开密码，得到题意求第n位（本身是素数，同时反过来也是素数的数）

题解：打表

注意：数组开大，反过来的数不能是自己本身

Description
qd ucyhf yi q fhycu dkcruh mxeiu huluhiu yi q tyvvuhudj fhycu dkcruh. oekh jqia yi je vydt jxu djx ucyhf.

Input
jxu ydfkj sediyiji ev q iydwbu ydjuwuh d (1 ≤ d ≤ 11184) — jxu edu-rqiut ydtun ev jxu ucyhf je vydt.

Output
ekjfkj q iydwbu dkcruh.

Sample Input
Input
1
Output
13

#include<stdio.h>
#include<math.h>

int a[11185];

int prime(int n)
{
    for(int i=2;i*i<=n;i++)
    {
        if(n%i==0)
            return 0;
    }
    return 1;
}

int mainn(int x)
{
    int sum=0;
    while(x)
    {
        sum=sum*10+x%10;
        x=x/10;
    }
    return sum;
}

int main()
{
    int i,k=1;
    for(i=12;i<=999998;i++)
    {
        if(prime(i)==1&&prime(mainn(i))==1&&i!=mainn(i))
        a[k++]=i;
    }
    int n;
    while(~scanf("%d",&n))
    {
        printf("%d
",a[n]);
    }
    return 0;
}