#include <fstream>
#include <cmath>
using namespace std;
ifstream f("DATE.IN");
ofstream g("date.out1");
int main()
{
    int  N,P,x,ld,ls,NMax,a,s,gasit;
    f>>P;
    if (P==0) g<<1;
    ls=5;
    ld=NMax;
    gasit=0;

    while(ls<=ld&&gasit==0)
        {
         NMax=(ld+ls)/2;
          x=0;
          a=s;
        while (a<=N)
        {
            x=x+N/a;
            a=a*5;
        }
    } while(x<P);
    if(x==P) g<<N;
             else g<<"-1";

return 0;
}