#include<iostream>
#include<queue>
#include<cstring>
#include<cstdio>
#define MAX 0x3f3f3f3f
using namespace std;
//const int maxn=2e5+7;
typedef long long ll;
const int maxn=105;

bool book[maxn];
int mon[maxn][maxn];
int d[maxn];
int mudi,T;
void spfa(int a)
{
    memset(book,false,sizeof(book));
    memset(d,MAX,sizeof(d));
    d[a]=0;
    queue<int>qu;
    qu.push(a);
    book[a]=true;
    int now;
    while(!qu.empty())
    {
        now=qu.front();
        qu.pop();
        book[now]=false;
        for(int i=1;i<=mudi;i++)
        {
            if(d[i]>d[now]+mon[now][i]) {
                d[i] = d[now] + mon[now][i];
                if (book[i] == 0) {
                    qu.push(i);
                    book[i] = true;
                }
            }
        }
    }
}
int main()
{
    while(scanf("%d%d",&mudi,&T))
    {
        if(mudi==0&&T==0)
            break;
        for(int i=1;i<=mudi;++i)
        {
            for(int j=1;j<=i;++j)
            {
                if(i==j)
                    mon[i][j]=0;
                else
                    mon[i][j]=mon[j][i]=MAX;
            }
        }
        int x,y,z;
        for(int i=1;i<=T;i++)
        {
            cin>>x>>y>>z;
            mon[x][y]=mon[y][x]=z;
        }
        spfa(1);
        printf("%d\n",d[mudi]);
    }
    return 0;
}