#include <iostream>
#include <fstream>

using namespace std;
ifstream fin ("fact.in");
ofstream fout ("fact.out");
int p,l,r,m,exp,x,sol;
bool ok=1;
int main()
{
    fin>>p;
    l=1;
    r=100000000;
    if (p==0)
        fout<<'1';
    else
    {
        while (l<=r && ok)
        {
            m=(l+r)/2;
            exp=0;
            x=m;
            while (x>0)
            {
                exp+=x;
                x/=5;
            }
            if (exp<p)
            {
                l=m+1;
            }
            else if (exp>p)
            {
                r=m-1;
            }
            else
            {
                ok=0;
                sol=m*5;
            }
        }
        if (ok)
            fout<<"-1";
        else fout<<sol;
    }
    return 0;
}