import std.stdio, std.string, std.conv; import std.range, std.algorithm, std.array, std.typecons, std.container; import std.math, std.numeric, core.bitop; alias Edge = Tuple!(int, "u", int, "v"); void main() { int n, x; scan(n, x); auto a = readln.split.to!(int[]); int[int] asc; long ans; foreach (i ; 0 .. n) { if (a[i] in asc) { ans += 2*asc[a[i]]; } if (a[i]*2 == x) { ans++; } if (x - a[i] in asc) { asc[x-a[i]]++; } else { asc[x-a[i]] = 1; } } writeln(ans); } struct UnionFind { private { int _size; int[] _parent; } this(int N) in { assert(N > 0); } body { _size = N; _parent = new int[](_size); foreach (i ; 0 .. _size) { _parent[i] = i; } } int findRoot(int x) in { assert(0 <= x && x < _size); } body { if (_parent[x] != x) { _parent[x] = findRoot(_parent[x]); } return _parent[x]; } bool same(int x, int y) in { assert(0 <= x && x < _size); assert(0 <= y && y < _size); } body { return findRoot(x) == findRoot(y); } void merge(int x, int y) in { assert(0 <= x && x < _size); assert(0 <= y && y < _size); } body { int u = findRoot(x); int v = findRoot(y); if (u == v) return; _parent[v] = u; } } void scan(T...)(ref T args) { import std.stdio : readln; import std.algorithm : splitter; import std.conv : to; import std.range.primitives; auto line = readln().splitter(); foreach (ref arg; args) { arg = line.front.to!(typeof(arg)); line.popFront(); } assert(line.empty); } void fillAll(R, T)(ref R arr, T value) { static if (is(typeof(arr[] = value))) { arr[] = value; } else { foreach (ref e; arr) { fillAll(e, value); } } }