def main():
    N, M = map(int, input().split())
    regions = []
    for _ in range(M):
        L, R = map(int, input().split())
        regions.append((L - 1, R - 1))
    regions.sort(key=lambda elm: elm[1])

    zero_ctr = 0
    zero_pos = -1
    for region in regions:
        if region[0] <= zero_pos <= region[1]:
            continue
        zero_pos = region[1]
        zero_ctr += 1
    print(N - zero_ctr)


if __name__ == "__main__":
    main()