#include <bits/stdc++.h>   using namespace std;   bool a[1000010];   int main() {     memset(a, 0, sizeof(a));     int n, ans = 0;     cin >> n;     int f = 2;     for (;;) {       if (a[f] == 0) {         for (int i = 2 * f; i <= 1000000; i = i + f) a[i] = 1;       }       f++;       if (f == 1000000) break;     }     for (int i = 10;; i++) {       int i1 = i, i2 = 0;       while (i1 > 0) {         i2 = i2 * 10 + i1 % 10;         i1 = i1 / 10;       }       if (a[i2] == 0 && a[i] == 0 && i2 != i) ans++;       if (ans == n) {         cout << i << endl;         return 0;       }     }     return 0;   }   