func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = 1e6 + 10;   const int mod = 1e9 + 7;   const int inf = 0x3f3f3f3f;   int a1[maxn], a2[maxn];   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     long long n, k;     cin >> n >> k;     long long ans = (n + 1) * n / 2;     for (int i = 1; i <= n; i++) a1[i] = i;     for (int i = 1; i <= n; i++) a2[i] = i;     if (ans > k) {       cout << -1 <<   n ;       return 0;     }     long long up = n / 2;     long long now = n - 1;     for (int i = 1; i <= up; i++) {       if (ans + now <= k) {         ans += now;         swap(a2[i], a2[i + now]);       } else {         swap(a2[i], a2[i + k - ans]);         ans = k;         break;       }       now -= 2;     }     cout << ans <<   n ;     for (int i = 1; i <= n; i++) cout << a1[i] << (i == n ?   n  :    );     for (int i = 1; i <= n; i++) cout << a2[i] << (i == n ?   n  :    );     return 0;   }   