program carz;
var
 a:array[1..10000]of real;
 b:array[1..10000]of integer;
 i,j,k,m,n,max,s,t:longint;
begin
 assign(input,'carz.in');reset(input);assign(output,'carz.out');rewrite(output);
 read(s,t);
 for i:=1 to s do
  begin
    if i<=10 then b[i]:=100;
    if (i>10)and(i<=20) then b[i]:=90;
    if (i>20)and(i<=30) then b[i]:=80;
    if (i>30)and(i<=40) then b[i]:=75;
    if i>40 then b[i]:=70;
  end;
 a[s]:=s/b[s];
 writeln(a[s]:0:2);
 close(input);close(output);
end.