1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <string>
 5 #include <algorithm>
 6 #include <iomanip>
 7 #include <vector>
 8 #include <cmath>
 9 using namespace std;
10 int N, M;
11 #define maxn 105
12 #define INF 0x3f3f3f3f
13 int mp[maxn][maxn];
14 int dist[maxn], vis[maxn];
15 void dijkstra(){
16     for(int i = 1; i <= N; i++) dist[i] = INF;
17     memset(vis, 0, sizeof(vis));
18     dist[1] = 0; 
19     vis[1] = 1;
20     
21     int pos = 1;
22     for(int i = 1; i <= N; i++){
23         int min = INF;
24         for(int j = 1; j <= N; j++){
25             if(!vis[j] && dist[j] < min){
26                 pos = j; min = dist[j];
27             }
28         }
29         vis[pos] = 1;
30         for(int j = 1; j <= N; j++){
31             if(!vis[j] && dist[j] > dist[pos] + mp[pos][j] ){
32                 dist[j] = dist[pos] + mp[pos][j];
33             }
34         }
35     } 
36 }
37 int main(){
38     while(scanf("%d%d", &N, &M) && (N+M)){
39         for(int i = 1; i <= N; i++){
40             for(int j = 1; j <= N; j++) mp[i][j] = INF;
41         }
42         for(int i = 1; i <= M; i++){
43             int a, b, c;
44             scanf("%d%d%d", &a, &b, &c);
45             mp[a][b] = c;
46             mp[b][a] = c;
47         }
48         dijkstra();
49         printf("%d\n", dist[N]);
50     }
51     
52     return 0;
53 }