#include <bits/stdc++.h>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int p;
unsigned long long int no_of_0(int k)
{
    unsigned long long int nr=0,product=5;
    while(product<=k)
    nr+=k/product,product*=5;
    return nr;
}
int binary_search()
{
    unsigned long long int q;
    int l=1,r=5*p,mid;
    while(l<r)
    {
        mid=l+r;
        mid/=2;
        q=no_of_0(mid);
        if(q>=p)
        r=mid;
        if(q<p)
        l=mid+1;
    }
    if(no_of_0(l)==p)
    return l;
    else return -1;
}
int main()
{
    in>>p;
    out<<binary_search();
    return 0;
}