N,Q = list(map(int,input().split())) L = [0] * Q R = [0] * Q for i in range(Q): L[i],R[i] = list(map(int,input().split())) lamp = [0] * (N+1) count = 0 for i in range(Q): for j in range(L[i],R[i] + 1): if lamp[j] == 1: count -= 1 lamp[j] = 0 else: count += 1 lamp[j] = 1 print(count)