https://www.acmicpc.net/problem/2563
시간 제한 : 1초
메모리 제한 : 128MB
n = int(input())
paper = [[0]* 101 for i in range(101)]
for _ in range(n):
x, y = map(int, input().split())
for i in range(10):
for j in range(10):
paper[x+i][y+j] = 1
result = 0
for i in paper:
result += sum(i)
print(result)