## https://qiita.com/embermaverick05/items/93b7258436c55b4a0528
class BIT:
    def __init__(self, N):
        self.N = N
        self.bits = [0] * (self.N + 1)
        
    def update(self, i, x):
        while i <= self.N:
            self.bits[i] += x
            i += i & -i
    
    def total(self, i):
        res = 0
        
        while i > 0:
            res += self.bits[i]
            i -= i & -i

        return res
    
N = int(input())
A = list(map(int, input().split()))
bit = BIT(N)
count = 0

# 座標圧縮
mapping = {a: i for i, a in enumerate(sorted(set(A)), start=1)}

# 転倒数のカウント
for i in range(N - 1, -1, -1):
    # 座標圧縮後の値（rank）を用いてBITに反映
    count += bit.total(mapping[A[i]] - 1)
    bit.update(mapping[A[i]], 1)
    
print(count)