#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], ndp[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;
	rep(i, n) ndp[i] = -INF;
	
	int ans = -INF;
	dp[0] = a[0];
	rep(i, 6 * n) {
		rep(j, n) {
			if (dp[j] <= -INF / 2) continue;
			rep(k, et[j].size()) {
				int u = j, v = et[j][k], c = ec[j][k];
				int val = dp[u] + a[v] - c;
				if (val >= -INF / 2 && ndp[v] < val) {
					ndp[v] = val;
				}
			}
		}
		rep(j, n) dp[j] = ndp[j];
		//rep(j, n) ndp[j] = -INF;
		if (ans < dp[n - 1] && dp[n - 1] >= -INF / 2) {
			ans = dp[n - 1];
			if (i > 3 * n) {
				cout << "inf" << endl;
				return 0;
			}
		}
	}
	
	cout << ans << endl;
	return 0;
}