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)