program nucle;
var a:array[0..50,0..51]of int64;
    t,k,m,n:longint;
    j:int64;
begin
assign(input,'nucle.in');
reset(input);
assign(output,'nucle.out');
rewrite(output);
readln(n,m);
a[1,0]:=1;
a[1,1]:=1;
a[1,51]:=1;
for t:=2 to n do
  for k:=0 to t do
    begin
      if k=0 then a[t,k]:=1
      else if (t=m)and(k=m) then a[t,k]:=0
      else if k<=m then a[t,k]:=a[t-1,k]+a[t-1,k-1]
      else a[t,k]:=a[t-1,k]+a[t-1,k-1]-a[m-1,m-1];
      a[t,51]:=a[t,51]+a[t,k];
    end;
for t:=0 to n do
  j:=j+a[n,t];
writeln(a[n,51]);
close(output);
end.