#include using namespace std; #define DEBUG(x) cerr<<#x<<": "< #define vl vector #define vii vector< vector > #define vll vector< vector > #define vs vector #define pii pair #define pis pair #define psi pair #define pll pair template pair operator+(const pair &s, const pair &t) { return pair(s.first + t.first, s.second + t.second); } template pair operator-(const pair &s, const pair &t) { return pair(s.first - t.first, s.second - t.second); } template ostream& operator<<(ostream& os, pair p) { os << "(" << p.first << ", " << p.second << ")"; return os; } #define X first #define Y second #define rep(i,n) for(int i=0;i<(int)(n);i++) #define rep1(i,n) for(int i=1;i<=(int)(n);i++) #define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--) #define rrep1(i,n) for(int i=(int)(n);i>0;i--) #define REP(i,a,b) for(int i=a;i bool chmax(T &a, const T &b) { if (a bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; } #define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end()); const ll inf = 1000000001; const ll INF = (ll)1e18 + 1; const long double pi = 3.1415926535897932384626433832795028841971L; #define Sp(p) cout< struct DisjointSparseTable { using F = function< Semigroup(Semigroup, Semigroup) >; const F f; vector< vector< Semigroup > > st; DisjointSparseTable(const vector< Semigroup > v, const F f) : f(f) { int b = 0; while((1 << b) <= v.size()) ++b; st.resize(b, vector< Semigroup >(v.size(), Semigroup())); for(int i = 0; i < v.size(); i++) st[0][i] = v[i]; for(int i = 1; i < b; i++) { int shift = 1 << i; for(int j = 0; j < v.size(); j += shift << 1) { int t = min(j + shift, (int) v.size()); st[i][t - 1] = v[t - 1]; for(int k = t - 2; k >= j; k--) st[i][k] = f(v[k], st[i][k + 1]); if(v.size() <= t) break; st[i][t] = v[t]; int r = min(t + shift, (int) v.size()); for(int k = t + 1; k < r; k++) st[i][k] = f(st[i][k - 1], v[k]); } } } Semigroup query(int l, int r) { if(l >= --r) { if (l > r) return pii(inf, 0); else return st[0][l]; } int p = 31 - __builtin_clz(l ^ r); return f(st[p][l], st[p][r]); } }; signed main() { fio(); int n, k; cin >> n >> k; vi a(n); vector temp(n); map last_idx; rep (i, n) { cin >> a[i]; temp[i].first = a[i]; temp[i].second = 1; last_idx[a[i]] = inf; } // SegmentTree seg(temp, f, g, pii(inf, 0)); DisjointSparseTable seg(temp, f); vi next_idx(n); rrep (i, n) { next_idx[i] = last_idx[a[i]]; last_idx[a[i]] = i; } ll ans = 0; for (auto iiitr = last_idx.begin(); iiitr != last_idx.end(); iiitr++) { ll x = iiitr->first; ll y = k - x; if (last_idx.count(y) == 0) continue; pll now(0, 0); int pre = -1; int li = last_idx[x], ri = last_idx[y]; using P = pair; set

one, two; while (li != inf or ri != inf) { // DEBUG(pii(x, y)); // DEBUG(pii(li, ri)); // DEBUG(now); // DEBUG(ans); int ni; if (li <= ri) { ni = li; } else { ni = ri; } // pii mi = seg.query(pre + 1, ni + 1, 0, 0, seg.n); pll mi = seg.query(pre + 1, ni + 1); P add1(mi.first, pii(0, 0)), add2(mi.first, pii(0, 0)); auto itr = one.end(); while (true) { if (itr == one.begin()) break; itr--; if (itr->first < mi.first) break; if (mi.second > 1) { add2.second.first += itr->second.first; add2.second.second += itr->second.second; } else { if (mi.first == itr->first) { add2.second.first += itr->second.first; add2.second.second += itr->second.second; } else { add1.second.first += itr->second.first; add1.second.second += itr->second.second; } } now.first -= itr->second.first; now.second -= itr->second.second; // one.erase(itr); } while (true) { auto itr = one.end(); if (itr == one.begin()) break; itr--; if (itr->first < mi.first) break; one.erase(itr); } itr = two.end(); while (true) { if (itr == two.begin()) break; itr--; if (itr->first < mi.first) break; if (mi.second > 1) { add2.second.first += itr->second.first; add2.second.second += itr->second.second; } else { if (mi.first == itr->first) { add2.second.first += itr->second.first; add2.second.second += itr->second.second; } else { add1.second.first += itr->second.first; add1.second.second += itr->second.second; } } // two.erase(itr); } while (true) { auto itr = two.end(); if (itr == two.begin()) break; itr--; if (itr->first < mi.first) break; two.erase(itr); } now.first += add1.second.first; now.second += add1.second.second; if (add1.second.second > 0) one.insert(add1); if (add2.second.second > 0) two.insert(add2); if (ni == li) { P add(x, pii(ni, 1)); now.first += ni; now.second += 1; auto itr = one.lower_bound(P(x, pll(-INF, -INF))); if (itr != one.end() and itr->first == x) { add.second.first += itr->second.first; add.second.second += itr->second.second; one.erase(itr); } one.insert(add); li = next_idx[li]; } else { ans += -now.first + now.second * (ri + 1); ri = next_idx[ri]; } pre = ni; } } cout << ans << endl; }