{***} Var f:text;
          k,i:int64;
          p,s:longint;
          as1:boolean;

Begin
assign(f,'fact.in');reset(f);read(f,p);close(f);
s:=0;i:=1;k:=1;
while s<p do begin
        k:=k*i;inc(i);
        as1:=true;
        while as1 do
                if k mod 10 =0 then begin inc(s);k:=k div 10;end
                               else as1:=false;
        k:=k mod 1000;
        end;
assign(f,'fact.out');rewrite(f);write(f,i);close(f);
end.