#include <iostream>
#include <vector>
#include <queue>
#include <functional>
using namespace std;
const int maxn = 1e5 + 5;
const int INF = 2e9;
int n, m;
vector<pair<int, int>> graph[maxn];

void dijkstra(int start_node, int end_node) {
    vector<bool> visited(n, false);
    vector<int> shortest_distance(n, INF);

    shortest_distance[start_node] = 0;
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;

    pq.push({start_node ,0});

    while(!pq.empty()) {
        pair<int, int> p = pq.top();
        pq.pop();
        int current_node = p.first;
        int current_node_path = p.second;

        if(visited[current_node]) {
            continue;
        }

        if(current_node == end_node) {
            cout << current_node_path << endl;
            return;
        }
        visited[current_node] = true;

        for(pair<int, int> neighbour : graph[current_node]) {
            int neighbour_node = neighbour.first;
            int neighbour_weight = neighbour.second;

            if(!visited[neighbour_node] and current_node_path + neighbour_weight < shortest_distance[neighbour_node]) {
                pq.push({neighbour_node, current_node_path + neighbour_weight});
                shortest_distance[neighbour_node] = current_node_path + neighbour_weight;
            }
        }


    }

}
int main() {
    cin >> n >> m;

    for(int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;

        graph[a].push_back({b, c});
        graph[b].push_back({a, c});
    }

    dijkstra(0, 4);

    return 0;
}