#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;

#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define rep(i, a, b) for (int i = (a); i < (b); i++)

mt19937 rng(random_device{}());

struct DSU {
	vi par, cnt;
	DSU(int N): par(N), cnt(N, 1) {
		iota(all(par), 0);
	}
	int root(int x) {
		if (par[x] == x) return x;
		return par[x] = root(par[x]);
	}
	int merge(int x, int y) {
		x = root(x), y = root(y);
		if (x == y) return 0;
		if (cnt[x] < cnt[y]) swap(x, y);
		par[y] = x;
		cnt[x] += cnt[y];
		return 1;
	}
};

int main() {
	cin.tie(0)->sync_with_stdio(0);
	int n, m;
	cin >> n >> m;
	vector<tuple<int, int, int>> edges;
	for (int i = 0; i < m; i++) {
		int a, b, w;
		cin >> a >> b >> w;
		a--,b--;
		edges.emplace_back(w, a, b);
	}
	sort(begin(edges), end(edges));
	DSU dsu(n);
	for (auto [w, a, b]: edges) {
		if (dsu.merge(a, b)) {
			if (dsu.root(0) == dsu.root(n - 1)) {
				cout << w << endl;
				return 0;
			}
		}
	}
	cout << "NaN" << endl;
}