class BinaryIndexedTree(object):
    __slots__ = ["tree"]

    def __init__(self, size: int):
        self.tree = [0]*(size+1)

    def add(self, index: int, value: int):
        tree = self.tree

        while index < len(tree):
            tree[index] += value
            index += index & -index

    def sum(self, index: int):
        tree, result = self.tree, 0

        while index:
            result += tree[index]
            index -= index & -index

        return result


def euler_tour(tree):
    from collections import deque

    tree_size, euler_tour_size = len(tree), len(tree)*2-1
    edges = [[] for _ in [0]*tree_size]
    for origin, destination in enumerate(tree):
        if destination >= 0:
            edges[destination].append(origin)

    subtree_range = [[0, 0] for _ in [0]*tree_size]
    dq, index = deque([0]), 0
    pop, extend = dq.pop, dq.extend

    while index < euler_tour_size:
        index, v = index+1, pop()
        if not subtree_range[v][0]:
            subtree_range[v][0] = index
        else:
            subtree_range[v][1] = index
            continue

        dq.append(tree[v])
        if edges[v]:
            dq.extend(edges[v])
        else:
            subtree_range[v][1] = index

    return subtree_range


if __name__ == "__main__":
    N = int(input())
    tree = [-1] + list(map(int, input().split()))
    subtree_range = euler_tour(tree)
    bit = BinaryIndexedTree(2*N-1)
    ans = 0

    for start, end in subtree_range[::-1]:
        ans += bit.sum(end) - bit.sum(start-1)
        bit.add(start, 1)

    print(ans)