function Fact(x: integer): integer;
var i, r: integer;
begin
     r := 1;
     for i := 1 to x do
         r := r * i;
     result := r;
end;

var i, n, x: integer;
    r: real;
begin
     readln(x, n);
     for i := 3 to (2 * n) do
     begin
          if (i mod 2 = 0) then continue;
          r := r + Power(x, i) / Fact(i);
     end;
     i := i + 3;
     r := r - Power(x, i) / Fact(i);
     writeln(r);
end.