#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_ON(bit, i) (bit & (1LL << i))

typedef long long LL;
template<typename T> using V = std::vector<T>;
template<typename T> using VV = std::vector<std::vector<T>>;
template<typename T> using VVV = std::vector<std::vector<std::vector<T>>>;
template<typename T> using VVVV = std::vector<std::vector<std::vector<std::vector<T>>>>;

template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}

const int INF = 1 << 30;
const double EPS = 1e-9;
const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy4 = { 0, 1, 0, -1 }, dx4 = { 1, 0, -1, 0 };    // 4近傍（右, 下, 左, 上）
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };

using namespace std;

class Imos {
public:
    std::vector<int> line;
    std::vector<std::vector<int>> field;
    int mode = 0;

    // 1次元imos
    Imos(int N) {
        this->mode = 1;
        this->line.resize(N + 1, 0);
    }

    // 2次元imos
    Imos(int H, int W) {
        this->mode = 2;
        this->field.resize(H + 1, std::vector<int>(W + 1, 0));
    }

    // [left, right)に+1
    void add(int left, int right) {
        assert(left < right);
        line[left]++;
        line[right]--;
    }

    // 左上(y1, x1)から右下(y2, x2)に+1する
    // 半開区間なので(y2, x2)は含まない
    void add(int y1, int x1, int y2, int x2) {
        assert(y1 < y2);
        assert(x1 < x2);

        field.at(y1).at(x1)++;    // 左上
        field.at(y1).at(x2)--;    // 右上
        field.at(y2).at(x1)--;    // 左下
        field.at(y2).at(x2)++;    // 右下
    }

    void build() {
        if (mode == 1) {
            build1();
        }
        if (mode == 2) {
            build2();
        }
    }

    void debug() {
        if (mode == 1) {
            debug1();
        }
        if (mode == 2) {
            debug2();
        }
    }

private:
    void build1() {
        for (int i = 1; i < line.size(); ++i) {
            line[i] += line[i - 1];
        }
    }

    void build2() {
        // 横方向への累積和
        for (int y = 0; y < field.size(); ++y) {
            for (int x = 1; x < field.at(0).size(); ++x) {
                field.at(y).at(x) += field.at(y).at(x - 1);
            }
        }
        // 縦方向の累積和
        for (int y = 1; y < field.size(); ++y) {
            for (int x = 0; x < field.at(0).size(); ++x) {
                field.at(y).at(x) += field.at(y - 1).at(x);
            }
        }
    }

    void debug1() {
        for (int i = 0; i < line.size(); ++i) {
            std::cout << line.at(i) << " ";
        }
        std::cout << std::endl;
    }

    void debug2() {
        for (int y = 0; y < field.size(); ++y) {
            for (int x = 0; x < field.size(); ++x) {
                std::cout << field.at(y).at(x) << " ";
            }
            std::cout << std::endl;
        }
    }
};

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

    int N, M;
    cin >> N >> M;
    V<int> P(M);
    FOR(i, 0, M) {
        cin >> P[i];
        P[i]--;
    }
    V<LL> A(N), B(N), C(N);
    FOR(i, 0, N - 1) {
        cin >> A[i] >> B[i] >> C[i];
    }

    Imos imos(N);
    FOR(i, 0, M - 1) {
        int s = P[i];
        int e = P[i + 1];
        if (s < e) {
            imos.add(s, e);
        }
        else {
            imos.add(e, s);
        }
    }
    imos.build();

    LL ans = 0;
    FOR(i, 0, N - 1) {
        LL num = imos.line[i];
        ans += min(A[i] * num, B[i] * num + C[i]);
    }
    print(ans);

}


Measured memory_bytes: 6104