oj 1219（noip 2008 T 3）

#include<algorithm> 
#include<bitset>//跑两边遍 
#include<cctype>
#include<cerrno>
#include<clocale>
#include<cmath>
#include<complex>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<deque>
#include<exception>
#include<fstream>
#include<functional>
#include<limits>
#include<list>
#include<map>
#include<iomanip>
#include<ios>
#include<iosfwd>
#include<iostream>
#include<istream>
#include<ostream>
#include<queue>
#include<set>
#include<sstream>
#include<stack>
#include<stdexcept>
#include<streambuf>
#include<string>
#include<utility>
#include<vector>
#include<cwchar>
#include<cwctype>
using namespace std;
const int maxn = 1000009;
const int maxxn = 100009;

int tt = 0;
int n,m;
int sum[maxxn];
int ans = 0;
int h[maxxn];
int lmaxx[maxxn];
int lminn[maxxn];
int rmaxx[maxxn];
int rminn[maxxn];
int a[maxn];
int tot = 0;
int vv[maxxn];
int head[maxxn];
bool v[maxxn];
struct node {
	int fr,ver,Next,id;
};
node edge[maxn];
node ee[maxn];

void bfs (int s) {
	lminn[s] = a[s];
	lmaxx[s] = a[s];
	queue <int > q;
	q.push(s);
	v[s] = 1;
	vv[s]++;
	while (!q.empty()) {
		int x = q.front();
		q.pop();
		for (int i = head[x];i;i = edge[i].Next) {
			int y = edge[i].ver;
				if (ee[i].id == 2)  {
					lmaxx[y] = max(lmaxx[x],a[y]);
				//	cout << "OPOOOOOOOOOOOOOOOOOO" <<endl;
			//		cout << x <<' ' <<y <<' ' <<lmaxx[x] <<' ' <<lmaxx[y] <<endl; 
				}
			//	cout << "PPPOOOOOOOOOOOOOOOOOPPP" <<endl;
			//	cout << x <<' ' <<y <<' ' << lminn[x] <<' ' <<lminn[y] <<endl;
				lminn[y] = min(lminn[x],a[y]);
			if (v[y] == 0)	vv[y]++,q.push(y),v[y] = 1;
		}
	}
}
void bfs_ (int s) {
	rminn[s] = a[s];
	rmaxx[s] = a[s];
	queue <int > q;
	q.push(s);
	v[s] = 1;
	vv[s]++;
	while (!q.empty()) {
		int x = q.front();
		q.pop();
		for (int i = h[x];i;i = ee[i].Next) {
			int y = ee[i].ver;
	//			cout << "PPPPPPPPPPPPPPPP" <<endl;
	//			cout << x<<' ' <<y << ' '<<rmaxx[x] <<' ' <<rmaxx[y] <<endl;
				rmaxx[y] = max(rmaxx[x],a[y]);				
				if (ee[i].id == 2) {
			//		cout << "PPPPPPPPPPPPPPp" <<endl;
			//		cout << x <<' ' <<y <<' ' <<rminn[x] <<endl;
					rminn[y] = min(rminn[x],a[y]);
			//		cout << rminn[y] <<endl;
				}
			if (v[y] == 0)	vv[y]++,q.push(y),v[y] = 1;
		}
	}
}
inline int Read () {
	int xx = 0;
	int ff = 1;
	char ch = getchar();
	while (ch > '9' || ch < '0') {
		if (ch == '-') ff = -1;
		ch = getchar();
	}
	while (ch <= '9' && ch >= '0') {
		xx = (xx << 1) + (xx << 3) + ch - '0';
		ch = getchar();
	}
	return xx * ff;
}
inline void add (int x,int y,int z) {
	edge[++tot].fr = x; edge[tot].ver = y; edge[tot].Next = head[x]; head[x] = tot; edge[tot].id = z; 
}
inline void ddd (int x,int y,int z) {
	ee[++tt].fr = x; ee[tt].ver = y; ee[tt].Next = h[x]; h[x] = tt; ee[tt].id = z;
}

int main () {
	n = Read(); m = Read();
	for (int i = 1;i <= n;i++) {
		a[i] = Read();
	}
	for (int i = 1;i <= m;i++) {
		int aa = Read();
		int bb = Read();
		int cc = Read();
		add(aa,bb,cc);
		ddd(bb,aa,cc);
	}
	for (int i = 1;i <= n;i++) {
		lminn[i] = a[i];
		lmaxx[i] = a[i];
		rmaxx[i] = a[i];
		rminn[i] = a[i];
	}
	memset(vv,0,sizeof(vv));
	memset(v,0,sizeof(v));
	bfs_(n);
	memset(v,0,sizeof(v));
	bfs(1);
	for (int i = 1;i <= n;i++) {
		if(vv[i] == 2) {
		//	cout << "PPPPPPPPPPPPPPPP" <<endl;
		//	printf("%d %d %d %d %d\n",i,rmaxx[i],lminn[i],lmaxx[i],rminn[i]);
			sum[i] = max(rmaxx[i] - lminn[i],lmaxx[i] - rminn[i]);
			ans = max(ans,sum[i]);
		}
	}
	printf("%d\n",ans);
	return 0;
}