#include<cstdio>
#include<queue>
#include<vector>
#include<algorithm>

using namespace std;
const int maxn=100010,INF=2147483647;
int n,m,c[maxn],a[2][maxn],s;
vector<int> G[2][maxn];

bool cmp(int k,int x,int y){
    return k?x>y:x<y;
}
void SPFA(int s,int k){
    queue<int> q;
    a[k][s]=c[s],q.push(s);
    while(!q.empty()){
        int u=q.front();q.pop();
        for(int j=0;j<G[k][u].size();j++){
            int v=G[k][u][j];
            if(cmp(k,a[k][u],a[k][v])){
                a[k][v]=a[k][u],q.push(v);
                if(cmp(k,c[v],a[k][v]))
                    a[k][v] = c[v];
            }
        }
    }
}

int main() {
    freopen("trade.in","r",stdin);
    freopen("trade.out","w",stdout);
    scanf("%d %d",&n,&m);
    for(int i=1;i<=n;i++)
        scanf("%d",c+i);
    int x,y,z;
    for(int i=1;i<=m;i++){
        scanf("%d%d%d",&x,&y,&z);
        G[0][x].push_back(y),G[1][y].push_back(x);
        if(z>1) G[0][y].push_back(x),G[1][x].push_back(y);
    }
    for(int i=1;i<=n;i++)
        a[0][i]=INF,a[1][i]=0;
    SPFA(1,0);
    SPFA(n,1);
    for(int i=1;i<=n;i++)
        s=max(s,a[1][i]-a[0][i]);
    printf("%d\n",s);
    return 0;
}