#include <bits/stdc++.h>
// clang-format off
using namespace std; using ll=long long; using ull=unsigned long long; using pll=pair<ll,ll>; const ll INF=4e18;
void print0(){}; template<typename H,typename... T> void print0(H h,T... t){cout<<h;print0(t...);}
void print1(){print0("\n");}; template<typename H,typename... T>void print1(H h,T... t){print0(h);if(sizeof...(T)>0)print0(" ");print1(t...);}
void ioinit() { cout<<fixed<<setprecision(15); cerr<<fixed<<setprecision(6); ios_base::sync_with_stdio(0); cin.tie(0); }
#define debug1(a) { cerr<<#a<<":"<<a<<endl; }
#define debug2(a,b) { cerr<<#a<<":"<<a<<" "<<#b<<":"<<b<<endl; }
#define debug3(a,b,c) { cerr<<#a<<":"<<a<<" "<<#b<<":"<<b<<" "<<#c<<":"<<c<<endl; }
#define debug4(a,b,c,d) { cerr<<#a<<":"<<a<<" "<<#b<<":"<<b<<" "<<#c<<":"<<c<<" "<<#d<<":"<<d<<endl; }
// clang-format on

struct edg {
    ll id;
    ll u;
    ll v;
    ll c;
};
ll n;
vector<vector<edg>> edgmap(2502);
vector<edg> edges;

// 各ノードからゴール(n-1)に到達できるか判定
vector<bool> arrive(2502);
vector<bool> search_arrive(2502);
bool dfs_arrive(ll u) {
    if (u == n - 1) {
        return true;
    }
    if (search_arrive[u]) {
        return false;
    }
    search_arrive[u] = true;
    for (auto e : edgmap[u]) {
        if (dfs_arrive(e.v)) {
            return true;
        }
    }
    return false;
}

// s->各頂点の最長路
vector<ll> bf_max(ll s) {
    vector<ll> dp(n, -INF);
    dp[s] = 0;
    for (ll op = 0; true; op++) {
        if (op > n) {
            return vector<ll>();
        }
        bool updated = false;
        for (auto e : edges) {
            if (!arrive[e.u] || !arrive[e.v]) continue;  // ゴール(n-1)に到達できないノードは無視する
            if (dp[e.u] != -INF && dp[e.v] < dp[e.u] + e.c) {
                updated = true;
                dp[e.v] = dp[e.u] + e.c;
            }
        }
        if (!updated) break;
    }
    return dp;
}

int main() {
    ioinit();
    ll m;
    cin >> n >> m;
    vector<ll> a(n);
    for (ll i = 0; i < n; i++) {
        cin >> a[i];
    }
    for (ll e = 0; e < m; e++) {
        ll u, v, c;
        cin >> u >> v >> c;
        u--;
        v--;
        ll score = -c + a[v];
        edg ed = {e, u, v, score};
        edges.push_back(ed);
        edgmap[u].push_back(ed);
    }
    for (ll i = 0; i < n; i++) {
        search_arrive.resize(0);
        search_arrive.resize(n + 1);
        arrive[i] = dfs_arrive(i);
    }
    auto result = bf_max(0);
    if (result.size() == 0) {
        print1("inf");
    } else {
        print1(result[n - 1] + a[0]);
    }
    return 0;
}