#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int verif(int n)
{
    int s=0,p=5;
    while(p<n)
    {
        s+=n/p;
        p*=5;
    }
}
int main()
{
    int n,st=0,dr=200000000,p,x,nr,a;
    in>>p;
    if(p==0) out<<"1";
    else
    {
        int m=1;
    while(st<dr&&m)
    {
    x=(st+dr)/2;
    a=verif(x);
    if(a==p) {nr=x-x%5;
              m=0;}
              else
    if(a<p) st=x+1;
    else
            dr=x-1;

    }
    if(m==0) out<<nr<<"/n";
        else out<<-1<<"/n";
}
return 0;
}