n, m = map(int, input().split())
a = list(map(int, input().split()))

ans = [(a[0], 1)]
for i in range(m - 1):
    if a[i+1] == a[i] + 1:
        s, l = ans[-1]
        ans[-1] = (s, l + 1)
    else:
        ans.append((a[i+1], 1))

print(len(ans))
for s, l in ans:
    print(s, l)