#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int P, st, dr, mij;

int Nr0(int x)
{
    int s = 0;
    while(x)
    {
        s += x / 5;
        x /= 5;
    }
    return s;
}
int main()
{
    fin >> P;
    st = 1, dr = 5 * 1e8;
    if(P == 0)
    {
        fout << 1;
        return 0;
    }
    while(st <= dr)
    {
        mij = (st + dr) / 2;
        int x = Nr0(mij);
        if(x == P)
        {
            fout << mij - mij % 5;
            return 0;
        }
        else if(x > P)
            dr = mij - 1;
        else
            st = mij + 1;
    }
    fout << -1;
    return 0;
}