#include <bits/stdc++.h>
using namespace std; 
typedef long long i64; 
const int N = 1e6 + 5; 

int n; 
int a[N]; 
struct Fenwick {
    int C[N]; 
    inline void add(int x, int k) { for (; x <= n; x += x & -x) C[x] += k; }
    inline int sum(int x) { int r = 0; for (; x; x -= x & -x) r += C[x]; return r; }
} F; 

int main(void) {
    ios::sync_with_stdio(0); 
    cin >> n; 
    for (int i = 1; i <= n; ++i) cin >> a[i]; 
    // 需要求，期望更换栈顶次数
    i64 ans = n - a[1]; F.add(a[n], 1); 
    for (int i = n - 1; i >= 1; --i) {
        F.add(a[i], 1); 
        int u = a[i], v = a[i + 1]; 
        ans += n - i - F.sum(min(u, v)); 
    }
    cout << fixed << setprecision(5) << ans * 0.5 + n << "\n"; 
    return 0;
}