#include <iostream>
using namespace std;
const long long NMAX=1e18;
typedef long long ll;
ll nrCifre(ll x)
{
    ll rez=0;
    while(x)
    {
        rez+=x/5;
        x/=5;
    }
    return rez;
}
int main() {
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    ll dr, st, n;
    cin>>n;
    st=1;dr=NMAX;
    while(st<dr)
    {
        ll mij=(dr+st)/2;
        if(nrCifre(mij)<n)
            st=mij+1;
        else
            dr=mij;
    }
    if(nrCifre(st) == n){
            cout << st << '\n';
    }
    else{
            cout << -1 << '\n';
    }

    return 0;
}