def isin(a, b):
    if b >= a[0] and b <= a[1]:
        return 1
    else:
        return 0


def choose(minnum,maxnum, l):
    s = 0
    chose = []
    for i in range(minnum,maxnum):
        for j in range(len(l)):
            s = s + isin(l[j], i)
        chose.append(s)
        s = 0
    index = chose.index(max(chose))
    num = minnum+index
    new = []
    for j in range(len(l)):
        if not isin(l[j], num):
            new.append(l[j])
    return new


n = int(input())
l = []
l1=[]
l2=[]
for i in range(n):
    x = list(map(int, input().split()))
    l1.append(x[0])
    l2.append(x[1])
    l.append(x)
jh=0
delete=[]
for j in range(len(l)):
    for i in range(len(l1)):
        if l1[i]<=l[j][0]<=l2[i] or l1[i]<=l[j][1]<=l2[i]:
            jh=jh+1
    if jh==1:
        delete.append(l[j])
    jh=0
for i in range(len(delete)):
    l.remove(delete[i])
    l1.remove(delete[i][0])
    l2.remove(delete[i][1])
k = len(delete)
while len(l) > 0:
    l = choose(min(l1),max(l2), l)
    k = k + 1
print(k-1)