var aux,n,p,vb1,cinci:longint;
begin
assign(input,'fact.in');
assign(output,'fact.out');
reset(input);
rewrite(output);
readln(p);
vb1:=0;
while vb1=0 do
  begin
   inc(n);
   aux:=n;
   while aux mod 5=0 do
     begin
      aux:=aux div 5;
      inc(cinci);
     end;
   if p=cinci then begin write(n); break end;
  end;
close(input);
close(output);
end.