#include <iostream>
#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

int cinciar(int x)
{
    int nr = 0;
    while(x%5 == 0)
    {
        x/=5;
        nr++;
    }
    return nr;
}

int main()
{
    long long n, p = 0;
    f>>n;
    while (n>0)
    {
        p+=5;
        n-=cinciar(p);
    }
    if(p==0)
        g<<1;
    else g<<p;
}