# dataの長さは1番目からnを2進数にしたときのLSBに相当
class Binary_Indexed_Tree:
    def __init__(self, n) -> None:
        self._n = n
        self.data = [0] * (n+1)
        self.depth = n.bit_length()
    
    # al〜arに一律加算ならいもす法でlにx加算、r+1に-x加算すれば良い
    # aiの値の取得はiまでのsum

    def add(self, p, x) -> None:
        """任意の要素ai←ai+xを行う O(logn)"""
        # pのindexが0以上n-1以下を保証
        assert 0 <= p < self._n
        # 1-indexedに変換
        p += 1
        while p <= self._n:
            # 加算
            self.data[p-1] += x
            # LSBの加算
            p += p & (-p)
    
    # 区間[l, r)
    def sum(self, l, r) -> int:
        assert 0 <= l <= r <= self._n
        return self._sum(r) - self._sum(l)
    
    def _sum(self, d) -> int:
        sm = 0
        while d > 0:
            sm += self.data[d-1]
            # LSB減算
            d -= d & (-d)
        return sm

N = int(input())
BIT = Binary_Indexed_Tree(N+1)
M = [int(input()) for _ in range(N)]
M = M[::-1]
res = 0
for num in M:
    BIT.add(num, 1)
    res += BIT._sum(num)
print(res)