#include "bits/stdc++.h"

/*
#include "boost/multiprecision/cpp_int.hpp"
namespace mp = boost::multiprecision;
using i128=mp::cpp_int;
*/

using namespace std;
typedef long long ll;
typedef int64_t i64;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vvll> vvvll;
typedef vector<string> vs;
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<double> vd;
typedef vector<vd> vvd;
#define rep(i,a,n) for(int i=a;i<n;i++)
#define drep(i,a,n) for(int i=a;i>n;i--)
#define yes(ans) if(ans)cout<<"yes"<<endl;else cout<<"no"<<endl;
#define Yes(ans) if(ans)cout<<"Yes"<<endl;else cout<<"No"<<endl;
#define YES(ans) if(ans)cout<<"YES"<<endl;else cout<<"NO"<<endl;
#define iINF 1000000007
#define lINF 10000000000007
#define llINF 4000000000000000007
#define all(x) x.begin(),x.end()
#define so(x) sort(all(x))
#define re(x) reverse(all(x))
const double PI = acos(-1);

//ベルマンフォード
struct edges{
  ll from;
  ll to;
  ll cost;
};
using ve=vector<edges>;
bool bellman(ve &miti,ll s,vll &dist,ll m){ //返り値 なし(副作用 distが変わる)
  dist[s]=0;
  ll y=1;
  ll cnt=0;
  while(y){
    if(cnt>m){
        return 1;
    }
    y=0;
    for(auto i:miti){
      if(dist[i.from]+i.cost<dist[i.to]){
        dist[i.to]=dist[i.from]+i.cost;
        y=1;
      }
    }
    cnt++;
  }
  return 0;
}

int main(){
    ll n,m; cin>>n>>m;
    vll d(n); rep(i,0,n) cin>>d[i];
    
    ve miti(m);
    ll a,b,c;
    rep(i,0,m){
        cin>>a>>b>>c; a--; b--;
        miti[i]={a,b,c-d[a]};
    }
    
    vll dist(n,llINF);
    bool y=bellman(miti,0,dist,m);
    //cout<<dist[n-1]<<endl;
    if(y) cout<<"inf"<<endl;
    else cout<<d[n-1]-dist[n-1]<<endl;
}