program Fact;
var fin,fout:text;
    i,j,aux,n,m,p,zero,nr:longint;
begin
     assign(fin,'fact.in'); reset(fin); assign(fout,'fact.out'); rewrite(fout);

     readln(fin,p); zero:=0;

     if p = 0 then
     begin
         writeln(fout,1);
         Close(fout);
         Halt;
     end;

     nr:=0;
     while zero <> p do
     begin
          nr:=nr+5;
          aux:=nr;
          while aux mod 5 = 0 do
          begin
              inc(zero);
              aux:=aux div 5;
          end;
     end;

     if zero = p then writeln(fout,nr)
     Else writeln(fout,-1);

     close(fin); Close(fout);
end.