func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 3000 + 5;   struct node {     int val, id;   } a[N];   int n;   int dp[N * N], tree[N], ranks[N];   inline int lowbit(int x) { return x & -x; }   inline int query(int x) {     int sum = 0;     while (x != 0) {       sum += tree[x];       x -= lowbit(x);     }     return sum;   }   inline void update(int x, int v) {     while (x <= n) {       tree[x] += v;       x += lowbit(x);     }     return;   }   bool cmp(node a, node b) {     if (a.val == b.val) return a.id < b.id;     return a.val < b.val;   }   signed main() {     cin >> n;     for (int i = 1; i <= n; i++) {       cin >> a[i].val;       a[i].id = i;     }     sort(a + 1, a + n + 1, cmp);     for (int i = 1; i <= n; i++) {       ranks[a[i].id] = i;     }     int ans = 0;     for (int i = 1; i <= n; i++) {       ans += (i - 1) - query(ranks[i]);       update(ranks[i], 1);     }     printf( %.6lf , (double)(2 * ans - (ans & 1)));     return 0;   }   