#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100010,MAXM = 500000 +10;

unordered_map<int,vector<int>> path;
unordered_map<int,vector<int>> rpath;
int price[MAXN];
int dp_max[MAXN],dp_min[MAXN];
int n,m;
void spfa(int start_point,int type) {
    queue<int> q;
    unordered_set<int> inq;
    // printf("start_point:=%d\n",start_point);
    if(type >0) {

        dp_min[start_point] = price[start_point];
    }else {

        dp_max[start_point] = price[start_point];
    }

    q.push(start_point);
    inq.insert(start_point);
    while(q.size()) {
        int u = q.front();q.pop(); inq.erase(u);
        //cout << u<<endl;
        if(type>0) {
            //求最小值
            for(int v: path[u]) {
                if(dp_min[v] >  min(dp_min[u] ,price[v] )  )
                {
                    dp_min[v] =  min(dp_min[u] ,price[v] ) ;
                    //  printf("v:=%d , %d\n",v,dp_min[v]);
                    if(inq.count(v)==false) {
                        inq.insert(v);
                        q.push(v);
                    }
                } 
            }
        }else {
            for(int v: rpath[u]) {
                if(dp_max[v] <  max(dp_max[u],price[v] ) )
                {
                    dp_max[v] =   max(dp_max[u],price[v] );
                    //  printf("r v:=%d , %d\n",v,dp_max[v]);
                    if(inq.count(v)==false) {
                        inq.insert(v);
                        q.push(v);
                    }
                }
            }

        }
    }

}
int main()
{

    cin>> n>>m;
    for(int i=1;i<=n;++i)
        cin>> price[i];
    // for(int i = 1; i <= n; i ++)
    // {
    //     //cin >> value[i];
    //     dp_min[i] = 999999999;
    //     dp_max[i] = -999999999;//先取一下极值，也就是初始化
    // }
    memset(dp_min,0x3f,sizeof dp_min);
    memset(dp_max,-0x3f,sizeof dp_max);
    //path.clear();
    //rpath.clear();
    while (m -- ) {
        int a,b,c;
        cin>> a>>b>>c;
        // path[a].push_back(b);
        // rpath[b].push_back(a);
        // if(c == 2) {
        //     path[b].push_back(a);
        //     rpath[a].push_back(b);
        // }
        if(c==2) {
            path[a].push_back(b);
            path[b].push_back(a);
            rpath[a].push_back(b);
            rpath[b].push_back(a);
        }else {
            path[a].push_back(b);
            rpath[b].push_back(a);
        }
    }
    spfa(1,1);
    spfa(n,-1);
    int res = 0;
    for(int i=1;i<=n;++i) 
    {
        // printf("dp_max[%d] = %d\n",i,dp_max[i]);
        // printf("dp_min[%d] = %d\n",i,dp_min[i]);

        res = max(res, dp_max[i] -dp_min[i]);
    }

    printf("%d\n",res);
    //cout << 0x3f<<endl;

    return 0;
}