#include<iostream>
#include<fstream>
using namespace std;
long P,N,p,a,b;
int put(long a, long N)
{
    while((N%a)==0){
                    N=N/a;
                    b++;
                    }
    return b;
}
int main()
{
    ifstream in("fact.in");
    ofstream out("fact.out");
    in>>P;
    if(P==0) out<<1<<endl;
    else{
         while(p<P){
                    N=N+5;
                    p=p+put(5,N);
                    }
         if(p==P) out<<N<<endl;                  
         else out<<-1<<endl;
         }    
    in.close();
    out.close();
    return 0;
}