#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("-Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-funroll-all-loops,-fpeel-loops,-funswitch-loops")
#define IO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define ll long long
const long long MOD = 1e9 + 7, OO = 1e18;
const double PI = acos(-1);
const int N = 1e6 + 5;
const int dx[8] = {0, 0, 1, -1, 1, 1, -1, -1};
const int dy[8] = {1, -1, 0, 0, 1, -1, 1, -1};

ll n, m, pl[N], u, v, mem[N][2][2][2][2];
pair<ll, ll>plant[N];

ll dp(ll i, bool pre, bool curr, bool first, bool final)
{
    ll &ret = mem[i][pre][curr][first][final];
    if (~ret)return ret;

    if (i == n)
    {
        if (final == 1)return 0;
        ll c1 = OO, c2 = OO;
        if (pre)c1 = pl[n - 1];
        if (first)c2 = pl[n];
        ret = min(c1, c2);
    }
    else 
    {
        ll c1 = OO, c2 = OO, c3 = OO;
        if (plant[i].first)
        {
            if (i == 1)first = 1;
            c1 = plant[i].second + dp(i + 1, 1, 0, first, final);
        }
        if (pre && curr == 0)
        {
            ll prev = i - 1;
            if (prev == 0)prev = n;
            if (i == 1)first = 0;
            c2 = pl[prev] + dp(i + 1, 0, 0, first, final);
        }
        if (curr == 0 && plant[i + 1].first && !(i + 1 == n && final == 0))
        {
            if (i == 1)first = 0;
            c3 = pl[i] + dp(i + 1, 0, 1, first, final);
        }
        ret = min({c1, c2, c3});
    }

    return ret;
}   

int main()
{
    IO  
    memset(mem, -1, sizeof mem);
    cin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        cin >> u >> v;
        plant[u] = {1, v};
    }
    for (int i = 1; i <= n; i++)cin >> pl[i];
    cout << min(dp(1, 0, 0, 0, 0), plant[n].second * plant[n].first + dp(1, plant[n].first, 0, 0, plant[n].first));
    return 0;   
}