#pragma comment(linker, "/STACK:189721600")
#include <iostream>
#include <fstream>
#include <set>
#include<iterator>
#include<vector>
#include <functional>
#include<queue>

using namespace std;
int main() {
	ifstream fin("input.txt");
	int n, m;
	fin >> n;
	fin >> m;
	ofstream fout("output.txt");
	pair<int, int> p;
	int x;
	vector<long long> d(n + 1, ULONG_MAX);
	struct Node
	{
		int v;
		long long len;
		Node(int v, long long len)
		{
			this->v = v;
			this->len = len;

		}
		bool operator >(const Node &n) const
		{
			return len > n.len;
		}
	};
	int y, h;
	vector<pair<int, int>> vct[200002];
	priority_queue<Node, vector<Node>, greater<Node> > q;
	for (int i = 0; i < m; i++) {
		fin >>x>> y >> h;
		vct[x].push_back(make_pair(y, h));
		vct[y].push_back(make_pair(x, h));
	}
	int flags[200001];
	d[1] = 0;
	q.push(Node(1, 0));
	for (int i = 1; i < n+1; i++)
	{
		flags[i] = false;
	}
	while (!q.empty())
	{
		Node node = q.top();
		q.pop();
		if (!flags[node.v])
		{
			flags[node.v] = true;
			for (auto j : vct[node.v])
			{
				if (node.len != ULONG_MAX &!flags[j.first] && node.len + j.second < d[j.first])
				{
					d[j.first] = node.len + j.second;
					q.push(Node(j.first, d[j.first]));
				}
			}
		}
	}
	fout << d[n];
	fout.close();}