import std;

int calc(int n, int k) {
    return 2^^n / 2^^k;
}

int calc2(int n, int k) {
    if (n >= k) return 2 ^^ (n - k);
    return 0;
}

void main() {
    int n, k; scan(n, k);
    writeln(calc2(n, k));
}

void scan(T...)(ref T a) {
    string[] ss = readln.split;
    foreach (i, t; T) a[i] = ss[i].to!t;
}
T read(T)() { return readln.chomp.to!T; }
T[] reads(T)() { return readln.split.to!(T[]); }
alias readint = read!int;
alias readints = reads!int;