#include<fstream>
using namespace std;
int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    long int N=1,P,i,j,nr=0;
    fin>>P;
    for(i=1;nr<100000000;i++)
                     {N=1;
                     nr=0;
                     for(j=1;j<=i;j++)
                                     N=N*j;
                     if(N%2==0 && N%5==0)
                                         while(N%2==0 && N%5==0)
                                                                {N=N/2;
                                                                N=N/5;
                                                                nr++;
                                                                }
                     if(nr==P)
                              {fout<<i;
                              fin.close();
                              fout.close();
                              return 0;
                              }
                     }
    fout<<-1;
    fin.close();
    fout.close();
    return 0;
}