#include //#include using namespace std; //using namespace atcoder; //using mint = modint1000000007; //const int mod = 1000000007; //using mint = modint998244353; //const int mod = 998244353; //const int INF = 1e9; //const long long LINF = 1e18; #define rep(i, n) for (int i = 0; i < (n); ++i) #define rep2(i,l,r)for(int i=(l);i<(r);++i) #define rrep(i, n) for (int i = (n-1); i >= 0; --i) #define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i) #define all(x) (x).begin(),(x).end() #define allR(x) (x).rbegin(),(x).rend() #define endl "\n" #define P pair template inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int n, x; cin >> n >> x; vectora(n); rep(i, n)cin >> a[i]; vectorleft(n), right(n); rep(_, 2) { long long sum = 0; int j = 0; for (int i = 0; i < n; ++i) { while (j < n && sum + a[j] <= x) { sum += a[j]; j++; } left[i] = j - i; sum -= a[i]; } reverse(all(a)); swap(left, right); } reverse(all(right)); // 手番の状態、勝ちなら1負けなら0を累積和で持つ vector dpl(n, vector(n + 2, 0)); vector dpr(n, vector(n + 2, 0)); rep2(i, 1, n + 1) { rep(j, n) { // 閉区間 int l = j; int r = l + i - 1; if (r >= n - 1)break; dpl[l][i + 0] = dpl[l][i - 1]; dpr[r][i + 0] = dpr[r][i - 1]; { int can = min(i - 1, left[l]); int x = dpr[r][i - 1] - dpr[r][i - can - 1]; if (x != can) { dpl[l][i + 0]++; dpr[r][i + 0]++; continue; } } int can = min(i - 1, right[r]); int x = dpl[l][i - 1] - dpl[l][i - can - 1]; if (x != can) { dpl[l][i + 0]++; dpr[r][i + 0]++; } } } if (dpl[0][n + 0] == dpl[0][n - 1])cout << "B" << endl; else cout << "A" << endl; return 0; }