#include <fstream>

using namespace std;

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    int n,p,c2,c5, x;
    f>>p;
    n = 1;
    c2 = c5 = 0;
    while(p > 0){
     n++;
     x = n;
     while(x % 10 == 0){
         p--;
         x = x / 10;
     }
     while(x % 2 == 0){
       c2++;
       x = x / 2;
     }
     while(x % 5 == 0){
      c5++;
      x = x / 5;
     }
     while(c2 > 0 && c5 > 0){
      c2--;
      c5--;
      p--;
     }
    }
    g<< n;
    return 0;
}