#include <bits/stdc++.h>
using namespace std;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

const int INF = 474'747'474;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, p;
	cin >> n >> p;
	vector<int> t(n), l(p), r(p);
	for (int& ti : t) {
		cin >> ti;
	}
	FOR(i, 0, p) {
		cin >> l[i] >> r[i];
	}
	p++;
	l.push_back(INF);
	r.push_back(INF + 1);
	vector charge(p, vector<int>(n));
	FOR(i, 0, p) {
		int j = i, s = 0;
		FOR(x, 0, n) {
			if (t[x] < l[i]) {
				continue;
			}
			while (l[j + 1] <= t[x]) {
				s += r[j] - l[j];
				j++;
				assert(j + 1 < p);
			}
			charge[i][x] = s + min(t[x], r[j]) - l[j];
		}
	}
	vector f(p, vector<int>(p));
	vector<int> lastPoint(p);
	FOR(j, 0, p) {
		lastPoint[j] = lower_bound(ALL(t), l[j]) - t.begin() - 1;
	}
	FOR(i, 0, p) {
		FOR(j, i + 1, p) {
			int firstPoint = j == 0 ? 0 : lastPoint[j - 1] + 1;
			int low = 0, high = n + 1;
			while (high - low > 1) {
				int mid = (low + high) / 2;
				bool ok = false;
				FOR(pt, max(mid - 1, firstPoint), lastPoint[j] + 1) {
					ok |= charge[i][pt - mid + 1] > t[pt] - t[pt - mid + 1];
				}
				if (ok) {
					low = mid;
				}
				else {
					high = mid;
				}
			}
			f[i][j] = low;
		}
	}
	vector dp(p, -INF);
	dp[0] = 0;
	FOR(i, 0, p) {
		FOR(j, i + 1, p) {
			dp[j] = max(dp[j], dp[i] + f[i][j]);
		}
	}
	cout << dp.back() + n << "\n";
	return 0;
}