#include <iostream>
#include <fstream>
using namespace std;


ifstream f("fact.in");
ofstream g("fact.out");
int nr5(int x)
{
    int sum=0;
    while (x)
    {
        sum+=x/5;
        x/=5;
    }
    return sum;
}
#define cout g
int main()
{
   f>>p;
    s=1;d=100000000;
    while  (s<=d)
    {
        m=(s+d)/2;
        if(nr5(m)==p) {
            cout<<m<<'\n';
            return 0;
        }
    }
    return 0;
}