def max_teams(n, a, b):
    teams = 0
    last_used = 0

    for i in range(1, n + 1):
        if i > last_used:
            if i + 1 <= n and i + 1 <= b[i] and i + 2 <= n and i + 2 <= b[i]:
                teams += 1
                last_used = i + 2
            elif i + 1 <= n and i + 1 <= b[i] and a[i + 1] <= i:
                teams += 1
                last_used = i + 1

    return teams

# Read input
n = int(input())
a = [0] * (n + 1)
b = [0] * (n + 1)
for i in range(1, n + 1):
    a[i], b[i] = map(int, input().split())

# Solve and print output
print(max_teams(n, a, b))