var a:array[0..10000,0..10000]of real;
    f,g:text;
    r,y,x:longint;
    d:byte;
    c:real;
begin
assign(f,'pascal.in');
assign(g,'pascal.out');
reset(f);
read(f,r,d);
close(f);
for y:=0 to r do
        begin
                c:=1;
                for x:=0 to y do
                        begin
                                a[y,x]:=c;
                                c:=c*(y-x)/(x+1);
                        end;
        end;
rewrite(g);
write(g,a[r-1,d-1]:0:0);
close(g);
end.