n, m = map(int, input().split())
LR = [list(map(int, input().split())) for _ in range(m)]

LR.sort(key=lambda x: (x[1], x[0]))
I = [LR[0][1]]
for i in range(1, m):
    if LR[i][0] <= I[-1] <= LR[i][1]:
        continue
    I.append(LR[i][1])

print(n - len(I))