#include using namespace std; #define FOR(i,a,b) for(int i=(a);i<(b);i++) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() template inline bool chmax(A &a, B b) { if (a inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; } typedef unsigned long long ull; typedef long long ll; typedef pair pii; typedef pair pll; typedef pair P; const ll INF = 1ll<<29; const ll MOD = 1000000007; const double EPS = 1e-12; int main() { int n, k; cin >> n >> k; int ans = 0; REP(i, 1< a, b; REP(j, n) { if (i >> j & 1) a.push_back(j + 1); else b.push_back(j + 1); } if (a.empty() || b.empty()) continue; if (a.front() != k) continue; if (a.back() < b.front()) continue; ans++; } cout << ans << endl; return 0; }