program carz;
var
  i,j,s,t:longint;
  f:array[0..1000]of real;
  ans:real;
begin
  assign (input,'carz.in');
  reset (input);
  assign (output,'carz.out');
  rewrite (output);
    readln (s,t);
    f[0]:=0;
    for i:=1 to s div 10 do
      f[i]:=maxlongint;
    for i:=1 to s div 10 do
      for j:=0 to i-1 do
      begin
        if i-j=1 then
        begin
          if f[j]+0.1+t/60<f[i] then
            f[i]:=f[j]+0.1+t/60
        end;
        if i-j=2 then
        begin
          if f[j]+20/90+t/60<f[i] then
            f[i]:=f[j]+20/90+t/60
        end;
        if i-j=3 then
        begin
          if f[j]+30/80+t/60<f[i] then
            f[i]:=f[j]+30/80+t/60
        end;
        if i-j=4 then
        begin
          if f[j]+40/75+t/60<f[i] then
            f[i]:=f[j]+40/75+t/60
        end;
        if i-j>4 then
        begin
          if f[j]+(i-j)*10/70+t/60<f[i] then
            f[i]:=f[j]+(i-j)*10/70+t/60
        end
      end;
    ans:=f[s div 10];
    ans:=ans-t/60;
    writeln (ans:0:2);
  close (input);
  close (output)
end.