hdu2544

#include <iostream>  //第一道用Dijkstra解的题
#include <cstring>
using namespace std;

#ifndef ONLINE_JUDGE
#include <fstream>
ifstream fin("test.txt");
#define cin fin
#endif
int n,m;
const int INF = 1000010;
int vis[200],dis[200];
int graph[200][200];
int main()
{
    ios::sync_with_stdio(false);
    int a,c,b;
    while(cin >> n >> m)
    {
        if(!n && !m)
        break;
        memset(vis,0,sizeof(vis));
        for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= n; ++j)
        {
            if(i==j)
            graph[i][j] = 0;
            else
            graph[i][j] = INF;
        }
        for(int i = 1; i <= m; ++i)
        {
            cin >> a >> b >> c;
            graph[a][b] = graph[b][a] = c;
        }
        for(int i = 1; i <= n; ++i)
        {
            dis[i] = graph[i][1];
        }
        vis[1] = 1;
        for(int i = 0; i < n; ++i)
        {
            int min = INF,t = 0;
            for(int j = 2; j <= n; ++j)
            if(!vis[j] && dis[j] < min)
            {
                min = dis[j];
                t = j;
            }
            vis[t] = 1;
            for(int j = 1; j <= n; ++j)
            {
                if(!vis[j] && dis[j] > dis[t] + graph[t][j])
                dis[j] = dis[t] + graph[t][j];
            }
        }
        cout << dis[n] << endl;
    }
    return 0;
}