#include <bits/stdc++.h>

using namespace std;

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


#define int long long

int nrzero(int x)
{
    int put5 = 5; int zero = 0;

    while(put5 <= x)
    {
        zero += x / put5;
        put5 *= 5;

    }
    return zero;
}

int  cb(int p,int n)
{
    int l = 1;
    int r = n;

    int rez = -1;
    while(l <= r)
    {
        int mid = (l + r) / 2;

        if(nrzero(mid) < p)
            l = mid + 1;
        else
        {
            if(nrzero(mid) == p)
                rez = mid;
                r = mid - 1;
        }
    }
    return rez;
}
 main()
{
    int p;

    in >> p;

    if(p == 0)
    {
        out << 1;
        return 0;
    }
    int n = 5 * p;
    out << cb(p,n);

    return 0;
}