N, Q = map(int, input().split())
LR = [list(map(int, input().split())) for _ in range(Q)]
la = [0] * N
for l, r in LR:
    la[l - 1] += 1
    la[r - 1] -= 1
    
ams = sum(i % 2 == 1 for i in la)
print(ans)