import sys
sys.setrecursionlimit(5*10**7)
import math
import bisect
import heapq
from collections import deque, defaultdict 
import random
import itertools
#from decimal import Decimal
#from copy import copy, deepcopy
#from sortedcontainers import SortedList

# -------------------------------------------------
pin = sys.stdin.readline
def ST(): return pin().rstrip()
def IN(): return int(pin())
def IM(): return map(int, pin().split())
def IL(): return list(IM())
def SR(n:int)->list: return [pin().rstrip() for _ in range(n)]
def IMatrix(n:int)->list: return [IL() for _ in range(n)]

INF = 2*10**18+1
mod = 998244353
# -------------------------------------------------
#import pypyjit
#pypyjit.set_param("max_unroll_recursion=-1")

N, M = IM()
A = IL() + [INF]

if M == 1:
	print(1)
	print(A[0], 1)
	exit()
	
ans = []

now = A[0]
cnt = 1

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

print(len(ans))
for i, j in ans:
	print(i, j)