#include <bits/stdc++.h>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int numar,n,x;
int main()
{
    f>>n;
    if(n==0)
        g<<1;
    else{
    int i=0;
        while(numar!=n)
            {
                i++;
                x=i;
                while(x%5==0)
                {numar++;
                x=x/5;
                }
            }
            g<<i;
}
}