N, M = map(int, input().split()) from collections import defaultdict L, R = defaultdict(int), defaultdict(int) for i in range(M): l, r = map(int, input().split()) L[l] += 1 R[r-1] += 1 n = 0 for i in range(N, 0, -1): n = n + L[i] - R[i] print(n)