#include<bits/stdc++.h>
using namespace std;

const int MAXN=5e4+5;
const int MAXM=1e5+5;
vector<pair<int,int> >e[MAXN];
int n,m,f[MAXN],minpr[MAXN],a[MAXN];

void dfs(int x,int minn,int last,int sum){
    int ff=1; 
    minn=min(a[x],minn);
    if(minpr[x]>minn){
    	minpr[x]=minn,ff=0;
    }
    int maxn=max(f[last],a[x]-minn-sum);
    if(f[x]<maxn){
    	f[x]=maxn,ff=0;
    }
    if(ff)return;
    for(int i=0;i<e[x].size();++i){
    	dfs(e[x][i].first,minn,x,sum+e[x][i].second);
    }
}

int main(){
	freopen("keepsake.in","r",stdin);
	freopen("keepsake.out","w",stdout);
	cin>>n>>m;
	for(int i=0;i<MAXN;++i)minpr[i]=1e9;
	int x,y,z;
	for(int i=1;i<=m;++i){
	    cin>>x>>y>>z;
		e[x].push_back(make_pair(y,z));
	}
	for(int i=1;i<=n;++i)cin>>a[i];
	dfs(1,1e9,0,0);
	cout<<f[n];
	return 0;
}