n, q = map(int, input().split()) sum = 0 a = [] for i in range(0, n): a.append(0) for i in range(0, q): l, r = map(int, input().split()) l -= 1 for j in range(l, r): if a[j] == 0: a[j] = 1 sum += 1 else: a[j] = 0 sum -= 1 print(sum)