#include <bits/stdc++.h>

typedef long double ld;
typedef long long ll;
using namespace std;
int di[] = {1, 0, -1, -1, 0, 1, -1, 1};
int dj[] = {1, 1, 0, -1, -1, 0, 1, -1};
const ll oo = 1e18, MOD = 998244353;
const int N = 2e5 + 5, M = 1e6 + 5;
const ld PI = acos(-1.0), EPS = 1e-9;

//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
//typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;

ll n, m, a[N], b[N], dp[N][2][2];

ll solve(int idx, int pre, int done) {
    if (idx > n) return 0;
    ll &ret = dp[idx][pre][done];
    if (~ret) return ret;
    ret = oo;
    if (a[idx] != oo) ret = min(ret, a[idx] + solve(idx + 1, 1, 1));
    if (pre) ret = min(ret, b[idx - 1] + solve(idx + 1, 1, 1));
    if (idx < n || done) ret = min(ret, b[idx] + solve(idx + 1, pre, done));
    return ret;
}

//#define endl '\n'
int main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    //freopen("farm.in", "r", stdin);
    memset(dp, -1, sizeof dp);
    cin >> n >> m;
    fill(a, a + N, oo);
    while (m--) {
        ll x, val;
        cin >> x >> val;
        a[x] = min(a[x], val);
    }
    for (int i = 1; i <= n; i++) cin >> b[i];
    cout << solve(1, 0, 0);
    return 0;
}