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

int main(void){
	int a[MAX],n;
	
	scanf("%d",&n);
	for(int i=0;i<n;i++)scanf("%d",&a[i]);
	
	llong ans=mergeSort(a,0,n);
	
	printf("%lld\n",ans);
	
	return 0;
}
