from sys import stdin

def main():
    NK = stdin.read().splitlines()

    players = ['you', 'grant']
    points = {'you': 0, 'grant': 0}
    for i, s in enumerate(NK):
        n, k = map(int, s.split())
        if i > 0 and n % k != 1:
            players[0], players[1] = players[1], players[0]
        if n % k == 1:
            points[players[0]] += 1
        else:
            points[players[1]] += 1
    print(points['you'])

main()