题解 | #剩下的树#
剩下的树
https://www.nowcoder.com/practice/f5787c69f5cf41499ba4706bc93700a2
l,m = input().split()
a = [input() for _ in range(int(m))]
b = [1]*(int(l)+1)
# print(len(b))
for i in range(int(m)):
for j in range(int(a[i].split()[0]),int(a[i].split()[1])+1):
b[j]=0
count = 0
for c in range(len(b)):
if b[c]==1:
count+=1
print(count)
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