#include <bits/stdc++.h>

using namespace std;

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

int nrzero(int n)
{
    int x,nr=0;
    x = 5;
    while(n / x != 0)
    {
        nr += n / x;
        x *= 5;
    }
    return nr;
}

int main()
{
    int n, p, st = 1, dr = 500000000, rasp=-1;
    fin >> p;
    if(p == 0)
    {
        fout << 1;
        return 0;
    }
    while(st <= dr)
    {
        int mij = (st + dr) / 2;
        int numar = nrzero(mij);
        if(p > numar)
            st = mij + 1;
        else if(p < numar)
            dr = mij - 1;
        else
        {
            rasp = mij - mij % 5;
            break;
        }
    }
    fout << rasp;
    return 0;
}