n,m = map(int,input().split())
L = []
for i in range(m):
    l,r = map(int,input().split())
    L.append([r,l])
L.sort()
ans = n
r = 0
if m != 1:
    while L[r+1][1] <= L[0][0]:
        r += 1
        if r == m-1:
            break
    ans -= 1

    for i in range(1,m):
        if i <= r:
            continue
        if r != m-1:
            while L[r+1][1] <= L[i][0]:
                r += 1
                if r == m-1:
                    break
            ans -= 1

else:
    ans = n-1
    
print(ans)