#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int k,num=1,fact,n=2,ok=1;
int main()
{
    f >> k;
    if (k==0)
        g << 1;
else {
   fact=k*5;
   while (ok!=0) {
     for (int i=1;i<=n;i++)
          num*=5;
     if (num<=fact) {
        fact-=5*(n-1);
        n++;
        num=1;
     }
    else
        ok=0;
   }

       g << fact;
}
    return 0;
}