#include #include #include #include #include #include #include #include #include #include #include #include #define vll vector #define vvvl vector #define vvl vector> #define VV(a, b, c, d) vector>(a, vector(b, c)) #define VVV(a, b, c, d) vector(a, vvl(b, vll (c, d))); #define re(c, b) for(ll c=0;c> n >> x; vll a(n);get(a);sort(all(a)); ll ans = 0; re(i, n){ ll need = x - a[i]; ll up = upper_bound(all(a), need) - a.begin(); ll dw = lower_bound(all(a), need) - a.begin(); ll cnt = up - dw; ans += cnt; } std::cout << ans << '\n'; return 0; }