#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int doi (int k)
{
    int ct=0;
    while (k%2==0)
    {
        k=k/2;
        ct++;
    }
    return ct;
}
int cinci (int k)
{
    int ct=0;
    while (k%5==0)
    {
        k=k/5;
        ct++;
    }
    return ct;
}
int main ()
{
    long int n=1,p,c2=0,c5=0,n1,n2;
    int i;
    f>>p;
    while (c2<=p)
    {
        c2=c2+doi(n);
        n++;
    }
    if (c2>p) n=n-2;
    n1=n-1;
    n=1;
    while (c5<=p)
    {
        c5=c5+cinci(n);
        n++;
    }
    if (c5>p) n=n-5;
    n2=n-1;
    if (n1>n2) g<<n1;
    else g<<n2;
}