Jamy

#include <bits/stdc++.h>

using namespace std;

#define MAX 100000
int arr[MAX + 1];

long long merge(int left, int mid, int right) {
    size_t m = mid - left + 1;
    size_t n = right - mid;
    int L[m], R[n];
    for(int i = left; i <= mid; ++i) L[i - left] = arr[i];
    for(int i = mid + 1; i <= right; ++i) R[i - mid - 1] = arr[i];

    int i = 0, j = 0, k = left;
    long long inversion = 0;
    while(i < m and j < n) {
        if(L[i] > R[j]) {
            inversion += m - i;
            arr[k++] = R[j++];
        } else {
            arr[k++] = L[i++];
        }
    }
    int l = i;
    while(i < m) {
        arr[k++] = L[i++];
    }
    while(j < n) {
        arr[k++] = R[j++];
    }
    return inversion;
}

long long mergeSort(int left, int right) {
    long long inversion = 0;
    if(left < right) {
        int mid = left + (right - left) / 2;
        inversion = mergeSort(left, mid);
        inversion += mergeSort(mid + 1, right);
        inversion += merge(left, mid, right);
    }
    return inversion;
}

int main(void) {
    freopen("input.txt", "r", stdin);
    int value;
    int indx = 0;
    while(scanf("%d", &value) != EOF) {
        arr[indx++] = value;
    }
    cout << mergeSort(0, MAX - 1);
    return 0;
}