N,M = map(int,input().split())
R = [[]]*M
for i in range(M):
  l,r = map(int,input().split())
  R[i] = [r+1,l]
  
R.sort()
ans=0
con_l=0
for i in range(M):
    if con_l <= R[i][1]:
        ans += 1
        con_l = R[i][0]
print(N-ans)