hdu 2544

#include"stdio.h"
#include"string.h"
#define M 111
#define inf 999999999
int G[M][M],dis[M],use[M];
int n;
void dij(int s)
{
    int i,k;
    memset(use,0,sizeof(use));
    for(i=1;i<=n;i++)
        dis[i]=G[i][s];
    dis[s]=0;
    use[s]=1;
    for(k=1;k<n;k++)
    {
        int min=inf,tep=-1;
        for(i=1;i<=n;i++)
        {
            if(!use[i]&&dis[i]<min)
            {
                min=dis[i];
                tep=i;
            }
        }
        use[tep]++;
        for(i=1;i<=n;i++)
        {
            if(!use[i]&&dis[i]>dis[tep]+G[i][tep])
            {
                dis[i]=dis[tep]+G[i][tep];
            }
        }
    }
}
int main()
{
    int m,i,j;
    while(scanf("%d%d",&n,&m),m||n)
    {
        for(i=1;i<=n;i++)
            for(j=1;j<=n;j++)
            {
                if(i==j)
                    G[i][j]=G[j][i]=0;
                else
                    G[i][j]=G[j][i]=inf;
            }
        while(m--)
        {
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            G[a][b]=G[b][a]=c;
        }
        dij(1);
        printf("%d\n",dis[n]);
    }
    return 0;
}