#include <stdio.h>

int prime(int value)
{
   unsigned int divisor = 3;
   unsigned int square  = divisor * divisor;

   if (value == 0)   return 0;
   if (value == 2)   return 1;
   if (value == 3)   return 1;
   if (!(value & 1)) return 0;	/* even */

   while (square < value && value % divisor) {
      ++divisor;
      square += 4 * divisor;
      ++divisor;
   }

   return value % divisor != 0;
}

int main() {
  char solved = 0;
  long long unsigned int n = 3;
  int a = 2;
  int i = 0;
  long long unsigned int sidelength = 3;
  long long unsigned int x = 0;
  long long unsigned int t = 0;
  
  while (! solved) {
    if (prime(n)) {
        x++;
    }
    t++;
    i++;
    if ((x * 1.0 / t * 1.0) < .1)
        solved = 1;
    
    if (i == 4 && ! solved) {
        i = 0;
        a += 2;
        sidelength+=2;
    }
    n += a;
  }
  printf("%llu\n",sidelength);
}