#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
//  by zrt
//  problem:uva10806
//  无论你在什么时候开始，重要的是开始以后就不要停止。
using namespace std ;
typedef long long LL ;
const double eps(1e-10) ;
const int inf(0x3f3f3f3f) ;
int H[105],X[40005],P[40005],from[40005],flow[40005],cost[40005],tot;
inline void add(int x,int y,int z,int k){
	P[++tot]=y;X[tot]=H[x];H[x]=tot;flow[tot]=z;from[tot]=x;cost[tot]=k;
}
int f,c;
int n,m;
int S,T;
int d[105],a[105],p[105];
struct N{
	int x,w;
	friend bool operator < (N a,N b){
		return a.w>b.w;
	}
	N(int a=0,int b=0){
		x=a,w=b;
	}
};
priority_queue<N> q;
bool spfa(){
	memset(d,0x3f,sizeof d);
	d[S]=0;a[S]=inf;p[S]=0;int x;
	q.push(N(S,0));
	while(!q.empty()){
		x=q.top().x;q.pop();
		if(x==T) continue;
		for(int i=H[x];i;i=X[i]){
			if(flow[i]>0&&d[P[i]]>d[x]+cost[i]){
				d[P[i]]=d[x]+cost[i];
				a[P[i]]=min(a[x],flow[i]);
				p[P[i]]=i;
				q.push(N(P[i],d[P[i]]));
			}
		}
		while(!q.empty()&&d[q.top().x]!=q.top().w) q.pop();
	}
	if(d[T]==inf) return 0;
	f+=a[T];
	c+=a[T]*d[T];
	x=T;
	while(x!=S){
		flow[p[x]]-=a[T];
		flow[p[x]^1]+=a[T];
		x=from[p[x]];
	}
	return 1;
}
int main(){
	#ifdef LOCAL
	freopen("in.txt","r",stdin) ;
	freopen("out.txt","w",stdout) ;
	#endif
	while(scanf("%d",&n)&&n){
		scanf("%d",&m);
		memset(H,0,sizeof H);f=c=0;tot=1;S=0,T=n;
		add(S,1,2,0);add(1,S,0,0);
		for(int i=0,x,y,z;i<m;i++){
			scanf("%d%d%d",&x,&y,&z);
			add(x,y,1,z);add(y,x,0,-z);
			add(y,x,1,z);add(x,y,0,-z);
		}
		while(spfa());
		if(f==2){
			printf("%d\n",c);
		}else{
			puts("Back to jail");
		}
	}
 
	return 0 ;
}