Program exer(input,output);
var N,i,p:integer;
    f:boolean;
begin
    readln(N);
    i:=1;
    p:=1;
    f:=false;
    while (not f) do
          begin
          p:=i*p;
          if (p>N) then
                 f:=true;
          else
               i:=i+1;
           end;
end.