c

#include<iostream>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<queue>
#include<climits>
#include<stdio.h>
using namespace std;
const int NV = 101;
const int inf = INT_MAX >> 1;
int m, n;int map[NV][NV];
int dis[NV];bool mark[NV];
int Spfa (int src, int des)
{
for (int i = 0; i <= n; i++)
{
mark[i] = false;
dis[i] = inf;
}
queue<int> Q;
mark[src] = true;
dis[src] = 0;
Q.push(src);
while (!Q.empty())
{
int first = Q.front();
Q.pop();
mark[first] = false;
for (int i = 1; i <= n; i++)
{
if (dis[first] + map[first][i] < dis[i])
{
if (!mark[i])
{
Q.push(i);
}
dis[i] = dis[first] + map[first][i];
mark[i] = true;
}
}//for
}//while
return dis[des];
}
int main()
{
while (~scanf("%d%d", &n, &m), n | m)
{
int a, b, c;
for (int i = 1; i <= n; i++)
{
map[i][i] = inf;
for (int j = i + 1; j <= n; j++)
{
map[i][j] = map[j][i] = inf;
}
}
while (m--)
{
scanf("%d%d%d", &a, &b, &c);
map[a][b] = map[b][a] = c;
}
printf("%d\n", Spfa(1, n));
}
return 0;
}