#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define rep2(i, s, n) for (ll i = s; i <= (ll)(n); i++)
#define rep3(i, s, n, d) for (ll i = s; i <= (ll)(n); i += d)
#define rep4(i, s, n, d) for (ll i = s; i >= (ll)(n); i += d)
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<vvvi> vvvvi;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<vvc> vvvc;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vvll> vvvll;
typedef vector<vvvll> vvvvll;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<vvd> vvvd;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<bool> vb;
typedef vector<vd> vvb;
typedef vector<vvd> vvvb;
typedef vector<pair<int, int>> vpi;
typedef vector<pair<ll, ll>> vpll;
typedef pair<int, int> pi;
typedef vector<pi> vpi;
typedef vector<vpi> vvpi;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;
typedef tuple<int, int, int> tui3;
typedef tuple<ll, ll, ll> tull3;
typedef priority_queue<int, vector<int>, greater<int>> pqi;
typedef priority_queue<vi, vector<vi>, greater<vi>> pqvi;
typedef priority_queue<ll, vector<ll>, greater<ll>> pqll;
typedef priority_queue<vll, vector<vll>, greater<vll>> pqvll;
typedef priority_queue<pll, vector<pll>, greater<pll>> pqpll;
typedef priority_queue<pll, vector<pll>, less<pll>> rpqpll;
typedef priority_queue<int, vector<int>, less<int>> rpqi;
typedef priority_queue<vi, vector<vi>, less<vi>> rpqvi;
typedef priority_queue<tui3, vector<tui3>, greater<tui3>> pqtui3;
typedef priority_queue<tui3, vector<tui3>, less<tui3>> rpqtui3;
typedef priority_queue<tull3, vector<tull3>, greater<tull3>> pqtull3;
typedef priority_queue<tull3, vector<tull3>, less<tull3>> rpqtull3;
#define yes(ans) if(ans)cout << "yes"<< endl; else cout << "no" << endl
#define Yes(ans) if(ans)cout << "Yes"<< endl; else cout << "No" << endl
#define YES(ans) if(ans)cout << "YES"<< endl ;else cout << "NO" << endl
#define printv(vec) {rep(i, vec.size()) cout << vec[i] << ' '; cout << endl;}
#define printvv(vec) rep(i, vec.size()) {rep(j, vec[i].size()) cout << vec[i][j] << ' '; cout << endl;};
#define printvvv(vec) rep(i, vec.size()) { rep(j, vec[i].size()) { rep(k, vec[i][j].size()) cout << vec[i][j][k] << ' '; cout << "	"; }cout << endl; };
#define all1(x) x.begin(),x.end()
#define all2(x) x.rbegin(), x.rend()
#define so(x) sort(all1(x))
#define re(x) reverse(all1(x))
#define rso(x) sort(all2(x))
#define vco(x, a) count(all1(x), a)
#define per(x) next_permutation(all1(x))
#define iINF 2147483647
#define llINF 9223372036854775807
#define INF 1000000000000000000
#define mod 998244353
#define mod2 1000000007

vi BFS(vvi& vec, int v0) {
    int n = vec.size();
    vi dist(n, mod);
    dist[v0] = 0;
    queue<int> que;
    que.push(v0);
    while (!que.empty()) {
        int v = que.front();
        que.pop();
        rep(i, vec[v].size()) {
            if (dist[vec[v][i]] < mod) continue;
            dist[vec[v][i]] = dist[v] + 1;
            que.push(vec[v][i]);
        }
    }
    return dist;
}

int main() {
    // アルゴリズム一覧を見る
    // 嘘解法ですか
    ll n, m; cin >> n >> m;
    vll vec(n);
    rep(i, n) cin >> vec[i];
    vvll list;
    vvi list2(n+1);
    rep(i, m){
        ll a, b, c; cin >> a >> b >> c;
        a--, b--;
        list.push_back({a, b, c-vec[a]});
        list2[b].push_back(a);
    }
    list.push_back({n-1, n, -vec[n-1]});
    list2[n].push_back(n-1);
    vi dist2 = BFS(list2, n);
    vll dist(n+1, INF);
    dist[0] = 0;
    ll cnt = 0;
    while(cnt<n+5){
        bool end = true;
        rep(i, list.size()){
            ll a = list[i][0];
            ll b = list[i][1];
            ll c = list[i][2];
            if(dist2[a]==mod || dist2[b]==mod) continue;
            if(dist[a]!=INF && dist[a]+c<dist[b]){
                dist[b] = dist[a]+c;
                end = false;
            }
        }
        if(end) break;
        cnt++;
    }
    if(cnt==n+5) cout << "inf" << endl;
    else cout << -dist[n] << endl;
}