#include<bits/stdc++.h>
using namespace std;
const int MAXN=1e5+5,INF=1e9+5;
int n,p,a[MAXN],f[MAXN],m[MAXN]; 
vector<int> v[MAXN];
void dfs(int x,int minn,int last){
	int flag=1;
	minn=min(a[x],minn);
	if(m[x]>minn)
		m[x]=minn,flag=0;
	int maxx=max(f[last],a[x]-minn);
	if(f[x]<maxx) f[x]=maxx,flag=0;
	if(flag) return;
	for(int i=0;i<v[x].size();i++)
		dfs(v[x][i],minn,x);
}
int main(){
	scanf("%d%d",&n,&p);
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
		m[i]=INF;
	}
	for(int i=1;i<=p;i++){
		int x,y,z;
		scanf("%d%d%d",&x,&y,&z);
		v[x].push_back(y);
		if(z==2)
			v[y].push_back(x);
	}
	dfs(1,INF,0);
	printf("%d",f[n]);	
}