#include<iostream>
#include<math.h>
#include<stdlib.h>
using namespace std;

int reverse(int num)
{
   int rev_num=0;
   while(num>0)
   {
      rev_num= rev_num*10 + num%10;
      num= num/10;
   }
   return rev_num;
}

bool isPrime(int num)
{
   int flag=1;
   if(num%2==0)
   {
      return false;
   }
   else
   {
      int limit= (int)(sqrt(num));
      int denom= 3;
      while(denom<=limit)
      {
         if(num%denom==0)
         {
            flag=0;
            return false;
         }
         else denom+=2;
      }
      return true;
   }
}



int main()
{
   int num;
   cin>>num;
   
   int flag=0;
   while(flag==0)
   {
      int rev_num = reverse(num);
      if(num-rev_num ==0)
      {
         bool ans = isPrime(num);
         if(ans== true)
            {
                cout<<num;
                flag=1;
            }
         else num++;
      }
      else num++;
   }
}