题解 | 校门外的树
校门外的树
https://www.nowcoder.com/practice/0e8cfc82936048769af45967f3c4ef7e
L,M=map(int,input().split())
tree=set(range(L+1))
for i in range(M):
l_i,r_i=map(int,input().split())
sube_i=set(range(l_i,r_i+1))
tree=tree-sube_i
print(len(tree))
