# 嘘解法。番兵を設置しない。

def main():
    N, M = map(int, input().split())
    A = list(map(int, input().split()))
    
    ans = []
    start = A[0]
    cnt = 1
    for i in range(M - 1):
        if A[i + 1] != A[i] + 1:
            ans.append((start, cnt))
            start = A[i + 1]
            cnt = 1
        else:
            cnt += 1
    
    print(len(ans))
    for start, cnt in ans:
        print(start, cnt)

if __name__ == '__main__':
    main()