#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
void binar(int p)
{
    long long s=1,e=100000,r=-1;


    int putere = 5;
    while(s<=e)
    {
        long long m;
        long long c=0;
        m=(s+e)/2;
        putere=5;
        while(putere <= m)
        {
            c += m / putere;
            putere *= 5;
        }
        if(c==p)
        {
            r=m;
            e=m-1;
        }
        else if(c<p)
        {
            s=m+1;
        }
        else if(c>p)
        {
            e=m-1;
        }
    }
    fout<<r<<endl;
}
int main()
{
    int p;
    fin>>p;
    binar(p);
    return 0;
}