N,M = list(map(int,input().split()))
A = list(map(int,input().split()))

ans = []
now = -100
count = 0
for i in range(M):
    if(A[i] == now+1):
        now += 1
        count += 1
    else:
        ans.append((now-count+1,count))
        now = A[i]
        count = 1
ans.append((now-count+1,count))
ans = ans[1:]

print(len(ans))
for i in ans:
    print(*i)