#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");
    int P;
void factorial()
{
    long long int nr=1, aux;
    unsigned int b=0;
    for(long int i=1;i<=25;i++){b=0;
                                nr=nr*i;
                                aux=nr;
                                while(aux%10==0){b++;
                                                 aux=aux/10;}
                                if(b==P){out<<i;
                                         break;}
                                else if(b>P)out<<"-1";}
}
    
int main()
{
    in>>P;
    factorial();
    return 0;
}