#include <bits/stdc++.h>
using namespace std;
long long n, m;
long long p[100005];
long long a[100005];
long long b[100005];
long long c[100005];
long long d[100005];
int main()
{
    cin >> n >> m;
    long long prev = 1;
    for (long long i = 1; i <= m; i++)
    {
        long long x;
        cin >> x;
        if (prev > x)
        {
            p[x + 1]++;
            p[prev + 1]--;
        }
        else
        {
            p[x + 1]--;
            p[prev + 1]++;
        }
        prev = x;
    }
    long long s = 0;
    for (long long i = 1; i <= n; i++)
    {
        s += p[i];
        d[i] = s;
    }
    for (long long i = 2; i <= n; i++)
    {
        cin >> a[i] >> b[i] >> c[i];
    }
    long long ans = 0;
    for (long long i = 2; i <= n; i++)
    {
        if (d[i] == 1)
        {
            ans += min(a[i], b[i] + c[i]);
        }
        else
        {
            ans += min(a[i] * d[i], b[i] * d[i] + c[i]);
        }
    }
    cout << ans;
    return 0;
}