#include <bits/stdc++.h>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int n,p;
int f2,f5,zero;
int main()
{
    in>>p;
    if(p==0)
    {
        out<<1;
        return 0;
    }
    zero=min(f2,f5);
    for(n=1;zero<p;n++)
    {
        int k=n;
        while(k%2==0)
        {
            k/=2;
            f2++;
        }
        while(k%5==0)
        {
            k/=5;
            f5++;
        }
        zero=min(f2,f5);
    }
    out<<n-1;
    return 0;
}