import sys
import queue
'''
input:
5
1 6
2 6
3 4
8 10
7 10
output:4
'''
if __name__ == "__main__":
N = int(sys.stdin.readline().strip())
postarr = []
arrlen = 0
for i in range(N):
line = sys.stdin.readline().strip().split()
if(arrlen<max(int(line[0]),int(line[1]))):
arrlen = max(int(line[0]),int(line[1]))
tmp = (int(line[0]),int(line[1]))
postarr.append(tmp)
arr = [0 for i in range(arrlen+1)]
for i in range(N):
tmp = postarr[i]
for j in range(tmp[0],tmp[1]+1):
arr[j] = i+1
a = set()
for i in range(1,arrlen+1):
a.add(arr[i])
print(len(a))