#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define ln cout<<'\n'
#define ll long long
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.12f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}void pr(){ln;}
template<class A,class...B>void pr(const A &a,const B&...b){cout<<a<<(sizeof...(b)?" ":"");pr(b...);}
template<class A>void PR(A a,ll n){rep(i,n)cout<<(i?" ":"")<<a[i];ln;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[8]={-1,0,1,0,-1,-1,1,1},dy[8]={0,1,0,-1,-1,1,1,-1};
typedef pair<ll,ll> P;

ll dp[2][2500];
vector<P> v[2500];

void Main() {
  ll n,m;
  cin >> n >> m;
  ll a[n];
  rep(i,n) cin >> a[i];
  rep(i,m) {
    ll x,y,z;
    cin >> x >> y >> z;
    x--,y--;
    v[x].pb(P(y,z));
  }
  rep(i,n) dp[0][i]=-MAXL;
  dp[0][0]=a[0];
  ll ans=-MAXL,t=0;
  rep(k,50000) {
    rep(i,n) {
      rep(j,v[i].size()) {
        ll x=v[i][j].F,c=v[i][j].S;
        dp[t^1][x]=max(dp[t^1][x],dp[t][i]+a[x]-c);
      }
    }
    fill(dp[t],dp[t]+n,-MAXL);
    t^=1;
    if(k>40000&&ans<dp[t][n-1]||dp[t][n-1]>MAXL) {
      pr("inf");
      return;
    }
    ans=max(ans,dp[t][n-1]);
    if(k>5000&&ans<0) break;
  }
  pr(ans);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}