题解 | 校门外的树
校门外的树
https://www.nowcoder.com/practice/0e8cfc82936048769af45967f3c4ef7e
L, M = map(int, input().split())
trees = [1] * (L + 1)
for i in range(M):
a, b = map(int, input().split())
for j in range(a, b + 1):
trees[j] = 0
print(sum(trees))
