/* -*- coding: utf-8 -*-
 *
 * 1604.cc:  No.1604 Swap Sort:ONE - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 3000;

/* typedef */

/* global variables */

int ps[MAX_N], tmp[MAX_N];

/* subroutines */

int merge_sort(int as[], int tmp[], int l, int r) { // [l, r)
  int ic = 0;

  if (l + 1 < r) {
    int m = (l + r) / 2;
  
    ic = merge_sort(as, tmp, l, m) + merge_sort(as, tmp, m, r);

    int i = l, j = m, k = l;

    while (i < m && j < r) {
      if (as[i] <= as[j]) tmp[k++] = as[i++];
      else tmp[k++] = as[j++], ic += m - i;
    }

    while (i < m) tmp[k++] = as[i++];
    while (j < r) tmp[k++] = as[j++];

    for (int i = l; i < r; i++) as[i] = tmp[i];
  }  

  return ic;
}

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", ps + i);

  int ic = merge_sort(ps, tmp, 0, n);
  printf("%d\n", ic);
  return 0;
}