#include #include #include using namespace std;

int main() { ios::sync_with_stdio(false); cin.tie(0);

int N, M;
cin >> N >> M;

vector<int> P(M);
for (int i = 0; i < M; i++) {
    cin >> P[i];
}

vector<int> A(N - 1), B(N - 1), C(N - 1);
for (int i = 0; i < N - 1; i++) {
    cin >> A[i] >> B[i] >> C[i];
}

// 统计每段铁路被经过的次数
vector<int> count(N - 1, 0);
for (int i = 1; i < M; i++) {
    int start = min(P[i - 1], P[i]) - 1;
    int end = max(P[i - 1], P[i]) - 1;
    for (int j = start; j < end; j++) {
        count[j]++;
    }
}

long long total = 0;
for (int i = 0; i < N - 1; i++) {
    long long ticket_cost = (long long)count[i] * A[i];
    long long ic_cost = C[i] + (long long)count[i] * B[i];
    total += min(ticket_cost, ic_cost);
}

cout << total << endl;

return 0;

}