#include <fstream>
#include <iostream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
unsigned P,N,in,i;
int k,j,b,b1;
int main()
{  f>>P;
   N=0;
   in=1;
   b=0;
    while(b<1)
    { k=0;
    N++;
    b1=0;
        for(i=1;i<=N;i++)
         in=in*i;

      while(b1<1)
      {
          if(in%10==0)k++;
          else if(in%10!=0) b1++;
          in=in/10;
      }
    if(k==P){j=N;b++;}
       in=1;
    }
    g<<N;
    return 0;
}