#include <iostream>
#include <fstream>
using namespace std;
ifstream f("factorial.in");
ofstream g("factorial.out");
int main()
{
int p,h=0;
    f>>p;
    if(p==0)g<<1;
    long long n=1;
    while (h<p)
    {
     h=0;
    for( int i=1;i<=n;i++)
    {long long aux=i;
    int k=0;
        while(aux%5==0)
        {
            k++;
            aux=aux/5;
        }
        h=h+k;

    }
    if(h==p) g<<n;
    else n++;
    }
}