C++ :

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

const int N = 1e5 + 5;
int n, m, p[N], a[N], b[N], w[N], ra[N], fa[N];
//vector < int > G[N];

int Get(int x)
{
//	printf("%d\n******", x);
	if (fa[x] == x) return x;
	return fa[x] = Get(fa[x]);
}

inline void Merge(int x, int y)
{
	int fx = Get(x), fy = Get(y);
	if (fx == fy) return;
	if (ra[fx] < ra[fy]) fa[fx] = fy;
	else
	{
		fa[fy] = fx;
		if (ra[fx] == ra[fy]) ++ra[fy];
	}
}

inline bool Check(int x)
{
	for (register int i = 1; i <= n; ++i)
		fa[i] = i;//, G[i].erase(G[i].begin(), G[i].end());
	memset(ra, 0, sizeof(ra));
	for (register int i = 1; i <= m; ++i)
		if (w[i] >= x) Merge(a[i], b[i]);
//	for (register int i = 1; i <= n; ++i)
//		G[Get(i)].push_back(i);
	for (register int i = 1; i <= n; ++i)
	{
//		writeln(i);
//		printf("%d %d\n", x, i); 
//		printf("%d %d\n", i, Get(i));
		if (Get(p[i]) != Get(i)) return 0;
	}
	return 1;
}

int main()
{
//	freopen("wormsort.in", "r", stdin);
//	freopen("wormsort.out", "w", stdout);
	scanf("%d%d", &n, &m);
	for (register int i = 1; i <= n; ++i)
		scanf("%d", p + i);
	for (register int i = 1; i <= m; ++i)
		scanf("%d%d%d", a + i, b + i, w + i);
//	if (n == 4 && m == 4 && p[1] == 3 && p[2] == 2 && p[3] == 1 && p[4] == 4) puts("9");
//	else puts("-1");
	int lft = 0, rgh = 1e9 + 2, ans = -1;
	while (lft <= rgh)
	{
		int md = (lft + rgh) >> 1;
		if (Check(md))
		{
			ans = md;
			lft = md + 1;
		}
		else rgh = md - 1;
	}
	if (ans == int(1e9 + 2)) ans = -1;
	printf("%d\n", ans);
	return 0;
}