n, m = map(int, input().split())
LR = []
for i in range(m):
    l, r = map(int, input().split())
    l, r = l-1, r-1
    LR.append((l, r))

LR.sort()
cnt = 0
curR = -1
for l, r in LR:
    if l <= curR:
        continue
    curR = r
    cnt += 1
print(n-cnt)