# coding: utf-8
# Your code here!
"""
Binary indexed tree
0-indexed, 関数は閉区間
0からの区間加算、1点更新
"""
class BIT: #0-indexed
    def __init__(self, n):
        self.tree = [0]*(n+1)
        self.tree[0] = None
#        self.element = [0]*(n+1)
    def sum(self, i): #a_0 + ... + a_{i} #閉区間
        s = 0; i += 1
        while i > 0:
            s += self.tree[i]
            i -= i & -i
        return s
    def range(self,l,r): #a_l + ... + a_r 閉区間
        return sum(r) - sum(l-1) 
    def add(self, i, x):
        i += 1
        while i <= n:
            self.tree[i] += x
            i += i & -i
        # self.element[i] += x
    #def get(self,i): return element[i]        
    
###########################################
import sys
sys.setrecursionlimit(10**6)
readline = sys.stdin.readline #文字列入力のときは注意

n,*a = map(int,open(0).read().split())

sA = sorted(a)
b = BIT(n)
from bisect import *
ans = 0
for i,ai in enumerate(a):
    j = bisect_left(sA, ai)
    ans += i - b.sum(j)
    b.add(j,1)

print(ans)