#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <queue>

using namespace std;

#define INF 0xfffffff

#define N 1002

bool vis[N];
int n, m, dist[N], G[N][N];

void Init()
{
    memset(vis, false, sizeof(vis));

    for(int i = 0; i <= n; i++)
    {
        dist[i] = INF;

        for(int j = 0; j <= n; j++)
            G[i][j] = G[j][i] = INF;
    }
}

int dij(int s, int e)
{
    dist[s] = 0;

    for(int i = 0; i <= n; i++)
    {
        int index = 0, Min = INF;

        for(int j = 0; j <= n; j++)
        {
            if(!vis[j] && dist[j] < Min)
                Min = dist[j], index = j;
        }

        vis[index] = true;

        for(int j = 0; j <= n; j++)
        {
            if(!vis[j] && dist[j] > dist[index] + G[index][j])
                dist[j] = dist[index] + G[index][j];
        }
    }
    return dist[e];
}

int main()
{
    int a, b, c;

    while(cin >> n >> m, n+m)
    {
        Init();

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

            G[a][b] = G[a][b] < c ? G[a][b] : c;
            G[b][a] = G[a][b];
        }
        cout << dij(1, n) << endl;
    }
    return 0;
}