from collections import defaultdict
n = int(input())
points = []
for _ in range(n):
a, b = map(int, input().split())
points.append((a, b))
points.sort()
# print(points)
res = 0
count = defaultdict(int)
for i in range(n):
x1, y1 = points[i]
count[x1-y1] += 1
for k, v in count.items():
if v == 1: continue
if v == 2:
res += 1
else:
n = v-1
res += max(0, (n * (n+1)) // 2)
print(res)
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