#include <bits/stdc++.h>

#define el '\n'
#define ll long long
#define ld long double

#define Beevo ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

using namespace std;

const ll INF = 1e18;

void testCase() {
    int n, m;
    cin >> n >> m;

    ll c;
    int u;
    vector<ll> cst(n + 1, INF), orgCst(n + 1, INF);
    for (int i = 0; i < m; i++) {
        cin >> u >> c;

        cst[u] = orgCst[u] = c;
    }

    for (int i = 1; i <= n; i++) {
        cin >> c;

        cst[i] = min(cst[i], c);

        if (i + 1 <= n)
            cst[i + 1] = min(cst[i + 1], c);
        else
            cst[1] = min(cst[1], c);
    }

    ll sum = 0;
    for (int i = 1; i <= n; i++)
        sum += cst[i];

    ll sol = INF;
    for (int i = 1; i <= n; i++)
        sol = min(sol, sum - cst[i] + orgCst[i]);

    cout << sol;
}

signed main() {
    Beevo

    int T = 1;
//    cin >> T;

    while (T--)
        testCase();

    return 0;
}