var n,m,i,p,d5:longint;
    f,g:text;
begin
assign(f,'fact.in');
assign(g,'fact.out');
reset(f);
read(f,p);
m:=1;
while d5<p do begin
      m:=m+1;
      n:=m;
      while n mod 5=0 do begin
            n:=n div 5;
            d5:=d5+1;
      end;
end;
rewrite(g);
if (d5=p) then write(g,m)
          else write(g,'-1');

close(f);
close(g);
end.