#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    int n;
    fin>>n;
    if(n==0) fout<<1;
    else {
        int pow5=0,r=0,aux;
        while(n>pow5)
        {
            r+=5,aux=r;
            while(aux%5==0)
            {
                pow5++;
                aux/=5;
            }
        }
        if(n<pow5) fout<<-1;
        else fout<<r;
    }
    return 0;
}