#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)

int main() {
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	
	int N, M;
	cin >> N >> M;
	vector<int> A(M);
	rep(i, 0, M) cin >> A[i];
	
	vector<pair<int, int>> ans;
	int cnt = 0;
	rep(i, 0, M) {
		if (i != 0 && A[i] - 1 != A[i - 1]) {
			ans.push_back({A[i - cnt], cnt});
			cnt = 0;
		}
		++cnt;
	}
	ans.push_back({A[M - cnt], cnt});
	
	cout << ans.size() << '\n';
	for (pair<int, int> t : ans) cout << t.first << ' ' << t.second << '\n';
}