#include <bits/stdc++.h>
#include <atcoder/all>
#define rep(i,a,n) for(ll i = a; i < n; i++)
#define yes (cout << "Yes" << endl)
#define YES (cout << "YES" << endl)
#define no (cout << "No" << endl)
#define NO (cout << "NO" << endl)
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define all(a)  (a).begin(),(a).end()
using namespace std;
using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vd = vector<double>;
using vs = vector<string>;
using vl = vector<long long>;
using vvi = vector<vector<int>>;
using Graph = vector<vector<int>>;
const int mod = 998244353;
const int MOD = 1000000007;
const int dx[4] = {-1,0,1,0};
const int dy[4] = {0,1,0,-1};
ll chmin(ll a,ll b) {
    if(a < b) return a;
    else return b;
}
void O(vector<int> v) {
    rep(i,0,v.size()) {
        cout << v[i] << " ";
    }
    cout << endl;
}
void O(vector<string> v) {
    rep(i,0,v.size()) cout << v[i] << endl;
    cout << endl;
}
void O(int a) {
    cout << a << endl;
}
void O(ll a) {
    cout << a << endl;
}
void O(string s) {
    cout << s << endl;
}
struct unionfind {
  vector<int> data;
  unionfind(int size) : data(size, -1) { }
  bool unite(int x, int y) {
    x = root(x); y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y);
      data[x] += data[y]; data[y] = x;
    }
    return x != y;
  }
  bool same(int x, int y) {
    return root(x) == root(y);
  }
  int root(int x) {
    return data[x] < 0 ? x : data[x] = root(data[x]);
  }
  int size(int x) {
    return -data[root(x)];
  }
};
ll gcd(ll a, ll b) {
	a = abs(a); b = abs(b);
	if (a < b)swap(a, b);
	while (b) {
		ll r = a % b; a = b; b = r;
	}
	return a;
}
//x,yがax+by=gcd(a,b)の解になる x,yが格納
ll extgcd(ll a, ll b, ll& x, ll& y) {
	ll d = a;
	if (b != 0) {
		d = extgcd(b, a % b, y, x);
		y -= (a / b) * x;
	}
	else {
		x = 1; y = 0;
	}
	return d;
}
ll pow(ll a,ll b) {
    ll ans = 1;
    rep(i,0,b) ans *= a;
    return ans;
}
int cnt = 0;
    int n,m;
    int a[200007];
    ll dp[200005];

    void dfs(const vector<vector<pair<int,int>>> &G,ll t) {
        for(auto p : G[t]) {
            ll k = p.fi;
            ll k2 = p.se;
            ll ori = dp[k];
            dp[k] = dp[t] - k2;
            if(ori == 0) dfs(G,k);
            if(1 <= ori && ori < dp[k]) {
                cout << "inf" << endl;
                cnt = 1;
                break;
            }
        }
    }
int main() {

    cin >> n >> m;

    rep(i,0,n) cin >> a[i];

    rep(i,0,n) dp[i] = 0;
    vector<vector<pair<int,int>>> G(n);
    rep(i,0,m) {
        int p,q,r;
        cin >> p >> q >> r;
        p--;
        q--;
        G[p].pb(mp(q,r));
    }
    dfs(G,0);
    if(cnt == 1) return 0;
    else {
        cout << dp[n - 1] << endl;
    }

}