#include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <tuple>
#include <cstdio>
#include <cmath>
#include <cassert>
#define rep(i, n) for(i = 0; i < n; i++)
#define int long long
using namespace std;

const int INF = 1e+16;
int n, m;
int a[2500];
vector<int> et[2500];
vector<int> ec[2500];
int dp[2500];

signed main() {
	int i, j, k;

	cin >> n >> m;
	rep(i, n) cin >> a[i];
	rep(i, m) {
		int u, v, c;
		cin >> u >> v >> c;
		u--; v--;
		et[u].push_back(v);
		ec[u].push_back(c);
	}
	rep(i, n) dp[i] = -INF;

	typedef pair<int, int> P;
	queue<P> que;
	int loopCnt = 0;

	que.push(P(a[0], 0));
	while (!que.empty()) {
		P now = que.front(); que.pop();
		int cst = now.first;
		int v = now.second;
		if (dp[v] >= cst) continue;
		dp[v] = cst;
		loopCnt++;

		if (loopCnt > 3 * n * n && v == n - 1) {
			cout << "inf" << endl;
			return 0;
		}

		for (int i = 0; i < et[v].size(); i++) {
			int nv = et[v][i];
			int nc = cst + a[nv] - ec[v][i];
			if (dp[nv] < nc) {
				que.push(P(nc, nv));
			}
		}
	}

	cout << dp[n - 1] << endl;
	return 0;
}