#include <bits/stdc++.h>
using namespace std;
#define forsn(i, s, n) for (int i = int(s); i < int(n); i++)
#define forn(i, n) forsn(i, 0, n)
#define dforsn(i, s, n) for (int i = int(n) - 1; i >= int(s); i--)
#define dforn(i, n) dforsn(i, 0, n)
#define qforn(i, n) for (i = 0; i < n; i++)
using vi = vector<int>;
using ii = pair<int, int>;
using vii = vector<ii>;
using ll = long long;
using ld = long double;
using vll = vector<ll>;
using vb = vector<bool>;
using pll = pair<ll, ll>;
#define sz(x) int(x.size())
#define all(x) begin(x), end(x)
#define pb push_back
#define eb emplace_back
#define fst first
#define snd second
const ll INF = 1e18;
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n, m;
cin >> m >> n;
vll p(m);
forn(i, m) cin >> p[i];
sort(all(p), greater<ll>());
vll dp(m + 1, INF);
dp[0] = 0;
forn(i, n) {
int c, e;
cin >> c >> e;
dforn(j, m + 1) dp[min(j + c, m)] = min(dp[min(j + c, m)], dp[j] + e);
}
ll ret = 0, pref = 0;
forn(i, m) {
pref += p[i];
ret = max(ret, pref - dp[i + 1]);
}
cout << ret << "\n";
return 0;
}
