#include <iostream>
#include <fstream>
#include <climits>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int nrciffact(int n)
{
    int s=0;
    for (int i=5; i<=n; i*=5) s+=n/i;
    return s;
}
int main()
{
    int p;
    in>>p;
    if (p==0)
    {
        out<<1;
        return 0;
    }
    int sf=INT_MAX,inc=0,mij;
    while (inc<sf)
    {
        mij=(inc+sf)/2;
        int x=nrciffact(mij);
        if (x<p) inc=mij+1;
        else sf=mij;
    }
    out<<inc;
}