#include<stdio.h>
#define MAX 500000
#define SENTINEL 2000000000

typedef long long llong;

int L[MAX/2+2],R[MAX/2+2];

llong merge(int A[], int n, int left, int mid, int right){
  int i,j,k;
  llong cnt = 0;
  int n1 = mid-left;
  int n2 = right - mid;
  for(i = 0; i < n1; i++) L[i] = A[left + i];
  for(i = 0; i < n2; i++) R[i] = A[mid + i];
  L[n1] = R[n2] = SENTINEL;
  j = 0;
  i = 0;
  for(k = left;k<right;k++){
    if(L[i] <= R[j]){
      A[k] = L[i++];
    }else{
      A[k] = R[j++];
      cnt+=n1-i;
    }
  }
  return cnt;
}


llong mergeSort(int A[], int n, int left, int right){
  int mid;
  llong v1,v2,v3;
  if(left+1<right){
    mid = (left+right)/2;
    v1 = mergeSort(A,n,left,mid);
    v2 = mergeSort(A,n,mid,right);
    v3 = merge(A,n,left,mid,right);
    return v1+v2+v3;
  }else return 0;
}


int main(){
  int A[MAX],n,i;
  llong cnt;
  cnt = 0;

  scanf("%d",&n);
  for(i = 0; i < n; i++) scanf("%d",&A[i]);

  llong ans = mergeSort(A,n,0,n);

  printf("%d\n",ans);
  return 0;
}

