Python贪心

n=int(input())
z=[]
num=1
for i in range(n):
    a=list(map(int,input().split()))
    z.append(a)
z.sort(key=lambda x: x[1])
k=z[0][1]
for i in range(len(z)):
    if z[i][0]>=k:
        k=z[i][1]
        num+=1
print(num)