#include<iostream>
#include<fstream>
using namespace std;
int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    int n,x=0,e=0,y;
    fin>>n;
    if(n==0) cout<<"1";
    else if(n<0) cout<<"-1";
    else
    {
        while(e<n)
        {
            x+=5;
            y=x;
            while(y%5==0)
            {
                e++;
                y/=5;
            }
        }
    }
    fout<<x;
}