#include <iostream>

#include <fstream>

using namespace std;

int nzero(int n)
{
    int nr5=0;
    while(n>=5)
    {
        nr5+=n/5;
        n=n/5;
    }
    return  nr5;
}

int caut(int x)
{
    int r=0, pas=1<<30;
    while(pas!=0)
    {
        if(nzero(r + pas) < x)
        {
            r+=pas;
        }
        pas=pas/2;
    }
    return r + 1;
}


int main()
{
    int p, n,i,pr=1;
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    cin>>p;

    cout<<caut(p);
    return 0;
}