#include <bits/stdc++.h>
using namespace std;
using lint = long long;

#line 2 "graph/shortest-path/bellman-ford.hpp"

#line 2 "graph/graph-template.hpp"

/**
 * @brief Graph Template(グラフテンプレート)
 */
template< typename T = int >
struct Edge {
  int from, to;
  T cost;
  int idx;

  Edge() = default;

  Edge(int from, int to, T cost = 1, int idx = -1) : from(from), to(to), cost(cost), idx(idx) {}

  operator int() const { return to; }
};

template< typename T = int >
struct Graph {
  vector< vector< Edge< T > > > g;
  int es;

  Graph() = default;

  explicit Graph(int n) : g(n), es(0) {}

  size_t size() const {
    return g.size();
  }

  void add_directed_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es++);
  }

  void add_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es);
    g[to].emplace_back(to, from, cost, es++);
  }

  void read(int M, int padding = -1, bool weighted = false, bool directed = false) {
    for(int i = 0; i < M; i++) {
      int a, b;
      cin >> a >> b;
      a += padding;
      b += padding;
      T c = T(1);
      if(weighted) cin >> c;
      if(directed) add_directed_edge(a, b, c);
      else add_edge(a, b, c);
    }
  }

  inline vector< Edge< T > > &operator[](const int &k) {
    return g[k];
  }

  inline const vector< Edge< T > > &operator[](const int &k) const {
    return g[k];
  }
};

template< typename T = int >
using Edges = vector< Edge< T > >;
#line 4 "graph/shortest-path/bellman-ford.hpp"

/**
 * @brief Bellman-Ford(単一始点最短路)
 * @docs docs/bellman-ford.md
 */
template< typename T >
vector< T > bellman_ford(const Edges< T > &edges, int V, int s) {
  const auto INF = numeric_limits< T >::max();
  vector< T > dist(V, INF);
  dist[s] = 0;
  for(int i = 0; i < V - 1; i++) {
    for(auto &e : edges) {
      if(dist[e.from] == INF) continue;
      dist[e.to] = min(dist[e.to], dist[e.from] + e.cost);
    }
  }
  for(auto &e : edges) {
    if(dist[e.from] == INF) continue;
    if(dist[e.from] + e.cost < dist[e.to]) return vector< T >();
  }
  return dist;
}


int main() {
  int n, m;
  cin >> n >> m;
  vector<lint> A(n);
  Edges< > es;
  for (int i = 0; i < n; i++) cin >> A[i];
  for (int i = 0; i < m; i++) {
    lint a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    es.push_back({a, b, -(A[a]-c)});
  }
  auto dists = bellman_ford(es, n, 0);
  if(dists.empty()) cout << "inf" << endl;
  else cout << -dists[n-1]+A[n-1] << endl;
}