Sending Emails

#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF (1<<29)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!\n");
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
#define IN(n) int n;scanf("%d",&n);
#define FOR(i, m, n) for (int i(m); i < n; i++)
#define REP(i, n) FOR(i, 0, n)
#define F(n) REP(i, n)
#define FF(n) REP(j, n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
void ga(int N,int *A){F(N)scanf("%d",A+i);}
#define MX (20000)
#define EG (100000)
#define TP (*q.begin())
int cn[MX],e[MX],g[EG],p[EG],V[EG],O;
void dj(int f){
    CL(cn,-1);cn[f]=0;
    set<ii> q={{0,f}};
    while(!q.empty()){
        int u(TP.bb),v(TP.aa);
        q.erase(TP);
        for(int d(e[u]);~d;d=p[d])
            if(!~cn[g[d]])q.insert({cn[g[d]]=V[d]+v,g[d]});
            else if(cn[g[d]]>V[d]+v)q.erase({cn[g[d]],g[d]}),q.insert({cn[g[d]]=V[d]+v,g[d]});
    }
}
#define ADD(A,B,W) (V[O]=W,p[O]=e[A],g[O]=B,e[A]=O++)
#define CLR (CL(e,-1),O=0)
int main(void){
    int a,b,c,N,M,f,t,cc(0);
    IN(tt)F(tt){
        scanf("%d%d%d%d",&N,&M,&f,&t),CLR;
        F(M)scanf("%d%d%d",&a,&b,&c),ADD(a,b,c),ADD(b,a,c);
        dj(f);
        if(~cn[t])printf("Case #%d: %d\n",++cc,cn[t]);
        else printf("Case #%d: unreachable\n",++cc);
    }
    return 0;
}