#include <bits/stdc++.h>
using namespace std;

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

long long cntZeros(long long n)
{
    long long z=0;
    while (n>0)
    {
        z += n/5;
        n /= 5;
    }
    return z;
}

int main()
{
    int p;
    fin>>p;
    if (p==0)
    {
        fout<<1;
        return 0;
    }

    long long l=0, r=10e15, mid, res=-1;
    while (l<=r)
    {
        mid = l+(r-l)/2;
        long long z=cntZeros(mid);
        if (z<p) l=mid+1;
        else if (z>p) r=mid-1;
        else
        {
            r=mid-1;
            res = mid;
        }
    }
    fout<<res;
}