HDU 2544

/*ACMer:MDK
2011-04-20 16:56:49	Accepted	2544	140 MS	4296 KB	GNU C++*/	
#include<iostream>
#include<string.h>
#include<limits.h>
#include<stdio.h>
#define MAXN 1005
#define INTMAX 1000000
using namespace std;
int map[MAXN][MAXN],minl[MAXN],pre[MAXN];
int big = INT_MIN;
int dijkstra(int N,int M,int s)
{
    int n = ++big,v[MAXN]={0},k,i,j;
    for(minl[s]=0,i = 0;i<n;i++)
    {
        for(k=-1,j = 0;j<n;j++)
            if(!v[j]&&(k==-1||minl[j]<minl[k]))
                k=j;
        for(v[k]=1,j = 0;j<n;j++)
            if(!v[j]&&map[k][j]+minl[k]<minl[j])
                minl[j]=map[k][j]+minl[k];  //一开始K打成J了，%>_<%，检查好久，不过一次AC了
    }
    return minl[N];
}
int main()
{
    //freopen("d:\\1.txt","r",stdin);
    int N,M;
    while(cin>>N>>M&&(N||M))
    {
        int a,b;
        memset(map,INTMAX,sizeof(map));
        memset(minl,INTMAX,sizeof(minl));
        memset(pre,0,sizeof(pre));
        for(int i = 0,v;i<M;i++){
            cin>>a>>b>>v;big = max(big,max(a,b));
            if( v < map[a][b] ) map[a][b] = map[b][a] = v;

        }//,cout<<map[b][a]<<endl;
        cout<<dijkstra(N,M,1)<<endl;
    }
}