n = int(input())
coordinate = []
count = 0

for i in range(n):
    coordinate.append(list(map(int, input().split())))

for i in range(n):
    for j in range(i + 1, n):
        if coordinate[i][0] == coordinate[j][0]:
            count += 1
        elif coordinate[i][1] == coordinate[j][1]:
            count += 1

print(count)