#include<fstream>
#include<cmath>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
unsigned long long int a[10000001],p,i,t=0,x=0,aux;
int main()
{


    fin>>p;
    a[1]=1;
    for(i=2;i<=5000000;i++)
    {
        t=0;
        aux=i;
        while(aux!=0)
        {
            if(aux%5==0)
            {
                t++;
            }
            else{
                break;
            }
            aux=aux/5;
        }
        a[i]=a[i-1]+1+t;
        if(a[i]==p)
        {
            x=1;
            fout<<i*5;
            break;
        }
    }
    if(x==0)
        fout<<-1;

}