class BIT:
    def __init__(self, size):
        self.size = size
        self.tree = [0] * (self.size + 1)
    
    def add(self, index, val):
        while index <= self.size:
            self.tree[index] += val
            index += index & -index
    
    def sum_query(self, index):
        res = 0
        while index > 0:
            res += self.tree[index]
            index -= index & -index
        return res

n = int(input())
M = [int(input()) for _ in range(n)]

bit = BIT(n)
ans = 0

for x in reversed(M):
    ans += bit.sum_query(x - 1)
    bit.add(x, 1)

print(ans)