#include<vector>
#include<cstdio>
#include<algorithm>
#define min(x,y) (((x)>(y))?(y):(x))
#define INF 0x3f3f3f3f
#define MAX_V 64+16
using namespace std;
struct edge
{
	int to,cap,cost,rev;
	edge(){}
	edge(int to1,int cap1,int cost1,int rev1)
	{
		to=to1;
		cap=cap1;
		cost=cost1;
		rev=rev1;
	}
};
int V;
vector<edge>G[MAX_V];
int dist[MAX_V];
int prevv[MAX_V],preve[MAX_V];
void add_edge(int from,int to,int cap,int cost)
{
	G[from].push_back(edge(to,cap,cost,G[to].size()));
	G[to].push_back(edge(from,0,-cost,G[from].size()-1));
}
int min_cost_flow(int s,int t,int f)
{
	int res=0,v;
	while(f>0)
	{
		fill(dist,dist+V,INF);
		dist[s]=0;
		bool update=true;
		while(update)
		{
			update=false;
			for(v=0;v<V;v++)
			{
				if(dist[v]==INF)
					continue;
				for(int i=0;i<G[v].size();i++)
				{
					edge &e=G[v][i];
					if(e.cap>0&&dist[e.to]>dist[v]+e.cost)
					{
						dist[e.to]=dist[v]+e.cost;
						prevv[e.to]=v;
						preve[e.to]=i;
						update=true;
					}
				}
			}
		}
		if(dist[t]==INF)
			return -1;
		int d=f;
		for(int v=t;v!=s;v=prevv[v])
			d=min(d,G[prevv[v]][preve[v]].cap);
		f-=d;
		res+=d*dist[t];
		for(v=t;v!=s;v=prevv[v])
		{
			edge &e=G[prevv[v]][preve[v]];
			e.cap-=d;
			G[v][e.rev].cap+=d;
		}
	}
	return res;
}
int main()
{
	int i,n,m,id=0;
	while(~scanf("%d%d",&n,&m))
	{
		V=n+2;
		if(n==0&&m==0)
			break;
		add_edge(0,1,2,0);
		add_edge(n,n+1,2,0);
		while(m--)
		{
			int a,b,c;
			scanf("%d%d%d",&a,&b,&c);
			add_edge(a+1,b+1,1,c);
		}
		int ans=min_cost_flow(0,n+1,2);
		printf("Instance #%d: ",++id);
        if(ans==-1)
            printf("Not possible\n");
		else
			printf("%d\n",ans);
		for(i=0;i<=n+1;i++)
			G[i].clear();
 
	}
	return 0;
}