#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("fact.in");
ofstream cout("fact.out");
long long n,m,i,j,k,st,dr,mid,sum,aux,s,p;
int main () {
    cin>>n;
    st=1;
    dr=9223372036854775807;
    aux=1;
    while (st<=dr) {
        mid=(st+dr)/2;
        p=5;
        aux=0;
        while (p<=mid) {
            aux+=mid/p;
            p*=5;
        }
        if (aux>=n) {
            dr=mid-1;
        }
        else {
            st=mid+1;
        }
    }
    p=5;
    aux=0;
    while (p<=st) {
        aux+=st/p;
        p*=5;
    }
    if (aux==n) {
        cout<<st;
    }
    else {
        cout<<"-1";
    }
}