#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
 
    ll N, M, A, B, C, start=0;
    ll from, to, c, alt, cnt=0;
    bool update;
    cin >> N >> M;
    vector<ll> v(N);
    for (int i=0; i<N; i++) cin >> v[i];
    vector<tuple<ll, ll, ll>> E(M);
    vector<vector<pair<ll, ll>>> ER(N);
    vector<ll> dist(N, 1e18);
    dist[start] = -v[0];
 
    for (int i=0; i<M; i++){
        cin >> A >> B >> C;
        A--; B--;
        E[i] = make_tuple(A, B, -v[B]+C);
        ER[B].push_back({A, i});
    }
    vector<bool> ok(M);

    auto dfs=[&](auto self, int from, int p)->void{
        for (auto [to, i] : ER[from]){
            if (to == p) continue;
            ok[i] = 1;
            self(self, to, from);
        }
    };
    dfs(dfs, N-1, -1);
 
    while(1){
        if (cnt == N){
            cout << "inf" << endl;
            return 0;
        }
        update = 0;
        for (int i=0; i<M; i++){
            if (!ok[i]) continue;
            tie(from, to, c) = E[i];
            alt = c + dist[from];
            if (dist[from] != 1e18 && alt < dist[to]){
                dist[to] = alt;
                update = 1;
            }
        }
        if (!update) break;
        cnt++;
    }

    cout << -dist[N-1] << endl;
 
    return 0;
}