#include <bits/extc++.h>

int main() {
    using namespace std;
    const auto find_shortest_path_cost{
        [](const unsigned N, const vector<tuple<unsigned, unsigned, long>> &edges, unsigned start, unsigned goal) -> optional<long> {
            constexpr auto inf{numeric_limits<long>::max()};
            vector<long> distance(N, inf);

            distance[start] = 0;
            for (unsigned j{}; j + 1 < N; j++)
                for (const auto &[from, to, cost] : edges)
                    if (distance[from] != inf && distance[to] > distance[from] + cost)
                        distance[to] = distance[from] + cost;

            for (unsigned i{}; i < N; i++)
                for (const auto &[from, to, cost] : edges)
                    if (distance[from] != inf && distance[to] > distance[from] + cost)
                        distance[to] = -inf;

            if (distance[goal] == -inf)
                return nullopt;
            return distance[goal];
        }};

    unsigned N, M;
    cin >> N >> M;

    vector<long> A(N);
    for (auto &a : A)
        cin >> a;

    vector<tuple<unsigned, unsigned, long>> edges(M);
    for (auto &[a, b, c] : edges) {
        cin >> a >> b >> c;
        --a;
        --b;
        c = c - A[a];
    }

    if (const auto ans{find_shortest_path_cost(N, edges, 0, N - 1)}; ans)
        cout << A.back() - *ans << endl;
    else
        cout << "inf" << endl;

    return 0;
}