#include <iostream>
#include <fstream>

using namespace std;

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

int n;

int zeros(int x)
{
    int p=5, k=0;
    while (p<=x)
    {
        k+=x/p;
        p*=5;
    }
    return k;
}

void binarySearch(int n)
{
    bool ok=0;
    int l=1, r=1<<30, mid;
    while (l<=r && !ok)
    {
        mid=(l+r)/2;
        int nr=zeros(mid);
        if (n==nr) { fout<<mid-mid%5; ok=1; }
        else if (n<nr) r=mid-1;
        else l=mid+1;
    }
    if (!ok) fout<<-1;
}

int main()
{
    fin>>n;
    if (!n) fout<<1;
    else binarySearch(n);
    return 0;
}