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// Online C++ compiler to run C++ program online
#include <iostream>
#include <vector>
#include <algorithm>
#include <unordered_map>

using namespace std;

long long merge(vector<long long>& arr, int l, int m, int r)
{
    int s1 = m - l + 1;
    int s2 = r - m;
    
    vector<long long> left(s1), right(s2);
    for (int i = 0; i < s1; i++)
        left[i] = arr[i + l];
    
    for (int i = 0; i < s2; i++)
        right[i] = arr[m + 1 + i];
    
    long long res = 0;
    int idx1 = 0, idx2 = 0;
    int k = l;
    while (idx1 < s1 && idx2 < s2)
    {
        if (left[idx1] <= right[idx2])
        {
            arr[k] = left[idx1];
            k++;
            idx1++;
        }
        else
        {
            arr[k] = right[idx2];
            k++;
            idx2++;
            res += s1 - idx1;
        }
    }
    
    while (idx1 < s1)
        arr[k++] = left[idx1++];
    while (idx2 < s2)
        arr[k++] = right[idx2++];
        
    return res;
}
long long count(vector<long long>& arr, int l, int r)
{
    long long res = 0;
    if (l < r)
    {
        int m = (r + l) / 2;
        
        res += count(arr, l, m);
        res += count(arr, m+1, r);
        res += merge(arr, l, m, r);
    }
    return res;
}

int main() {
    // Write C++ code here
    int n;
    cin >> n;
    
    vector<long long> nums(n);
    for (int i = 0; i < n; i++)
    {
        int t;
        cin >> t;
        
        nums[i] = t;
    }
    
    cout << count(nums, 0, n - 1);
    

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED

Test 41

Verdict: ACCEPTED

Test 42

Verdict: ACCEPTED

Test 43

Verdict: ACCEPTED

Test 44

Verdict: ACCEPTED

Test 45

Verdict: ACCEPTED

Test 46

Verdict: ACCEPTED

Test 47

Verdict: ACCEPTED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED

Test 50

Verdict: ACCEPTED

Test 51

Verdict: ACCEPTED

Test 52

Verdict: ACCEPTED

Test 53

Verdict: ACCEPTED

Test 54

Verdict: ACCEPTED

Test 55

Verdict: ACCEPTED

Test 56

Verdict: ACCEPTED

Test 57

Verdict: ACCEPTED

Test 58

Verdict: ACCEPTED

Test 59

Verdict: ACCEPTED

Test 60

Verdict: ACCEPTED

Test 61

Verdict: ACCEPTED

Test 62

Verdict: ACCEPTED

Test 63

Verdict: ACCEPTED

Test 64

Verdict: ACCEPTED

Test 65

Verdict: ACCEPTED

Test 66

Verdict: ACCEPTED

Test 67

Verdict: ACCEPTED

Test 68

Verdict: ACCEPTED

Test 69

Verdict: ACCEPTED

Test 70

Verdict: ACCEPTED

Test 71

Verdict: ACCEPTED