from sys import stdin

N, M = [int(x) for x in stdin.readline().split()]
a = []
for i in range(M):
	k, v = [int(x) for x in stdin.readline().split()]
	a.append([k,v])
a.sort()
b = [a[0]]
for i in range(1,M):
	elozo = a[i-1]
	most = a[i]
	if elozo[1] >= most[0]:
		b[-1][-1] = max(most[1],b[-1][-1])
	else:
		b.append(most)
eleje = 1
max_hossz = b[0][0]-1
for j in range(1,len(b)):
	hossz = b[j][0]-b[j-1][1]-1
	if hossz > max_hossz:
		max_hossz = hossz
		eleje = b[j-1][1]+1
if max_hossz == 0:
	print(-1)
else:
	print(max_hossz, eleje)