#include <bits/stdc++.h>

const int INF = 1E9 + 4;

int N, M;
std::vector<std::pair<int, int>> edge[310000];
std::vector<std::tuple<int, int, int>> tedge;
int ufs[310000];

int find(int x) {
	if (ufs[x] == x) return x;
	return ufs[x] = find(ufs[x]);
}

void merge(int x, int y) {
	x = find(x); y = find(y);
	if (x != y) ufs[x] = y;
}

int main() {
	scanf("%d%d", &N, &M);
	for (int i = 0; i < M; ++i) {
		int u, v, c;
		scanf("%d%d%d", &u, &v, &c);
		edge[u].push_back({v, c});
		edge[v].push_back({u, c});
		tedge.push_back({c, u, v});
	}
	for (int i = 1; i <= N; ++i) ufs[i] = i;
	std::sort(tedge.begin(), tedge.end());
	int ans = INF + INF;
	for (auto e: edge[1]) {
		if (e.first == N) ans = std::min(ans, e.second);
	}
	for (int i = 0; i < (int) tedge.size(); ++i) {
		int c, u, v; std::tie(c, u, v) = tedge[i];
		merge(u, v);
		if (find(1) == find(N)) break;
		if (find(u) == find(1)) {
			for (auto e: edge[u]) if (find(e.first) == find(N))
				ans = std::min(ans, e.second + c);
		}
		if (find(v) == find(1)) {
			for (auto e: edge[v]) if (find(e.first) == find(N))
				ans = std::min(ans, e.second + c);
		}
		if (find(u) == find(N)) {
			for (auto e: edge[u]) if (find(e.first) == find(1))
				ans = std::min(ans, e.second + c);
		}
		if (find(v) == find(N)) {
			for (auto e: edge[v]) if (find(e.first) == find(1))
				ans = std::min(ans, e.second + c);
		}
	}
	printf("%d\n", ans);
}