#include <stdio.h>
#include <math.h>
#include <string.h>
#define rad M_PI/3
#define N 500001

int S[N]={0};
int L[N/2]={0};
int R[N/2]={0};
long count =0;

void Merge(int A[],int left,int mid,int right){
    int n1,n2;
    int i,j,k;
    n1=mid-left;
    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]=1000000010;
    R[n2]=1000000010;
    i=j=0;
    for(k=left;k<right;++k){
        if(L[i]<=R[j]){
            A[k]=L[i];
            ++i;
    }else{
        A[k]=R[j];
        ++j;
        count+=(n1-i);
    }
    }
    return;
}
void MergeSort(int A[], int left, int right) {
    int mid;
    if (left + 1 < right) {
        mid = (left + right) / 2;
        MergeSort(A, left, mid);
        MergeSort(A, mid, right);
        Merge(A, left, mid, right);
    }
    return;
}

int main()
{
  int n, i;
 
    scanf("%d", &n);
 
    for (i = 0; i < n; ++i) {
        scanf("%d", &S[i]);
    }
    MergeSort(S, 0, n);
    printf("%ld\n", count);
     
    return 0;
  return 0;
}
