Go: package main

import (
	"container/heap"
	"fmt"
	"runtime"
)

type Node struct {
	NowPosition          int
	DiscountTicketTCount int
	Amount               int
}

type PriorityQueueNode []*Node

func (pq PriorityQueueNode) Len() int {
	return len(pq)
}

func (pq PriorityQueueNode) Less(i, j int) bool {
	return pq[i].Amount < pq[j].Amount
}

func (pq PriorityQueueNode) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
}

func (pq *PriorityQueueNode) Push(node interface{}) {
	*pq = append(*pq, node.(*Node))
}

func (pq *PriorityQueueNode) Pop() interface{} {
	old := *pq
	n := len(old)
	item := old[n-1]
	*pq = old[0 : n-1]
	return item
}

type Point struct {
	NextPoint int
	Fee       int
}

type Memo struct {
	NowPoint             int
	DiscountTicketTCount int
}

func main() {
	var c, n, m, s, d int
	var a, b, f int

	for {
		fmt.Scan(&c, &n, &m, &s, &d)
		if c == 0 && n == 0 && m == 0 && s == 0 && d == 0 {
			break
		}
		s--
		d--
		pointMap := make([][]Point, n)
		for i := 0; i < n; i++ {
			pointMap[i] = make([]Point, 0, n)
		}
		for i := 0; i < m; i++ {
			fmt.Scan(&a, &b, &f)
			a--
			b--
			pointMap[a] = append(pointMap[a], Point{NextPoint: b, Fee: f})
			pointMap[b] = append(pointMap[b], Point{NextPoint: a, Fee: f})
		}
		pq := make(PriorityQueueNode, 0, m)
		start := Node{NowPosition: s, DiscountTicketTCount: c, Amount: 0}
		heap.Push(&pq, &start)
		memo := make(map[Memo]int)
		for len(pq) != 0 {
			now := heap.Pop(&pq).(*Node)
			if now.NowPosition == d {
				fmt.Println(now.Amount)
				break
			}
			memo[Memo{NowPoint: now.NowPosition, DiscountTicketTCount: now.DiscountTicketTCount}] = now.Amount
			for _, v := range pointMap[now.NowPosition] {
				next := &Node{v.NextPoint, now.DiscountTicketTCount, now.Amount + v.Fee}
				if memoAmount, ok := memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}]; !ok || (ok && memoAmount > next.Amount) {
					memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}] = next.Amount
					heap.Push(&pq, next)
				}
				if now.DiscountTicketTCount > 0 {
					next = &Node{v.NextPoint, now.DiscountTicketTCount - 1, now.Amount + v.Fee/2}
					if memoAmount, ok := memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}]; !ok || (ok && memoAmount > next.Amount) {
						memo[Memo{NowPoint: v.NextPoint, DiscountTicketTCount: now.DiscountTicketTCount}] = next.Amount
						heap.Push(&pq, next)
					}
				}
			}
		}
		runtime.GC()
	}
}

C++: #include <map>
#include <vector>
#include <cstdio>
#include <cstring>
using namespace std;
int cost[101][11];
int main(){
	int c,N,m,s,d,i,j,k,x;
	for(;scanf("%d%d%d%d%d",&c,&N,&m,&s,&d),N;){
		vector<map<int,int> >dist(N+1);
		memset(cost,99,sizeof(cost));
		for(k=0;k<m;k++){
			scanf("%d%d%d",&i,&j,&x);dist[i][j]=dist[j][i]=x;
		}
		for(i=0;i<=c;i++)cost[s][i]=0;
		for(;~c;c--){
			vector<bool>used(N+1);
			for(;;){ //dijkstra
				int m=9999999;
				for(i=1;i<=N;i++)if(!used[i]&&m>cost[i][c])m=cost[i][c];
				if(m==9999999)break;
				for(j=1;j<=N;j++)if(m==cost[j][c]){
					map<int,int>::iterator it=dist[j].begin();
					for(used[j]=1;it!=dist[j].end();it++){
						if(cost[it->first][c]>it->second+cost[j][c])cost[it->first][c]=it->second+cost[j][c];
						if(c&&cost[it->first][c-1]>it->second/2+cost[j][c])cost[it->first][c-1]=it->second/2+cost[j][c];
					}
				}
			}
		}
		printf("%d\n",cost[d][0]);
	}
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1<<28

using namespace std;
typedef pair<int,int> P;


struct edge
{
	int to;
	int cost;

	edge(int to,int cost) : to(to),cost(cost) {}
};

int d[11][101];
vector<edge> G[101];

void dijkstra(int s,int n,int ticket)
{
	priority_queue<P,vector<P>,greater<P> > que;
	rep(i,n) d[i][ticket] = INF;
	d[s][ticket] = 0;
	que.push(P(0,s));

	while(!que.empty())
	{
		P p = que.top();
		que.pop();

		int v = p.second;
		if(d[v][ticket] < p.first) continue;

		rep(i,G[v].size())
		{
			edge e = G[v][i];
			int temp;

			if(ticket == 0)
			{
				temp = d[v][ticket] + e.cost;
			}
			else
			{
				temp =  min(d[v][ticket]+e.cost,d[v][ticket-1]+e.cost/2);
			}

			if(d[e.to][ticket] > temp)
			{
				d[e.to][ticket] = temp;
				que.push(P(d[e.to][ticket],e.to));
			}
		}
	}
}

int main()
{
	int c,n,m,s,t;
	while(cin >> c >> n >> m >> s >> t)
	{
		if(c == 0 && n == 0 && m == 0 && s == 0 && t == 0) break;
		
		s--;
		t--;
		rep(i,100) G[i].clear();

		rep(i,m)
		{
			int a,b,cost;
			cin >> a >> b >> cost;
			a--;
			b--;

			edge e(b,cost);
			G[a].push_back(e);

			edge e2(a,cost);
			G[b].push_back(e2);
		}
		
		rep(i,n) dijkstra(s,n,i);

		cout <<  d[t][c] << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <algorithm>
using namespace std;

#define MAX 100
#define INF 1000000
int G[MAX][MAX];
int c, n, m, s, d, a, b, f;

int dijkstra(){
    int D[MAX][11];
    bool visited[MAX][11];
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= c; j++) {
            D[i][j] = INF;
            visited[i][j] = false;
        }
    }
    D[s][c] = 0;
    while (true) {
        int u, w, minv = INF;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j <= c; j++) {
                if (!visited[i][j] && minv > D[i][j]) {
                    minv = D[i][j];
                    u = i;
                    w = j;
                }
            }
        }
        if (minv == INF) {
            break;
        }
        visited[u][w] = true;
        for (int v = 0; v < n; v++) {
            if (G[u][v] == INF) {
                continue;
            }
            D[v][w] = min(D[v][w], D[u][w] + G[u][v]);
            if (w) {
                D[v][w-1] = min(D[v][w-1], D[u][w] + G[u][v] / 2);
            }
        }
    }
    int minv = INF;
    for (int i = 0; i <= c; i++) {
        minv = min(minv, D[d][i]);
    }
    return minv;
}

int main()
{
    while (true) {
        cin >> c >> n >> m >> s >> d;
        if (s == 0 && d == 0) {
            break;
        }
        s--;
        d--;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                G[i][j] = INF;
            }
        }
        for (int i = 0; i < m; i++) {
            cin >> a >> b >> f;
            a--;
            b--;
            G[a][b] = G[b][a] = f;
        }
        cout << dijkstra() << endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define RFOR(i,a,b) for(int i=(b) - 1;i>=(a);i--)
#define REP(i,n) for(int i=0;i<(n);i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)

#define PB push_back
#define INF INT_MAX/3
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CLR(a) memset(a,0,sizeof(a))

typedef long long int ll;

using namespace std;

int c,n,m,s,d;
int rosen[101][101] = {-1};
int saiki(int p,vector<int> st,vector<bool> u){
    int ans = INF;
    if(p == d){
	sort(RALL(st));
	int tc = min(c,(int)(st.size()));
	REP(i,tc){
	    st[i] /= 2;
	}
	int sum = 0;
	REP(i,st.size()){
	    sum += st[i];
	}
	return sum;
    }
    FOR(i,1,n+1){
	if(!u[i] && rosen[p][i] > 0){
	    vector<int> temp = st;
	    vector<bool> utemp = u;
	    temp.PB(rosen[p][i]);
	    utemp[i] = true;
	    ans = min(ans,saiki(i,temp,utemp));
	}
    }
    return ans;
}

int main(){
    while(true){
	cin >> c >> n >> m >> s >> d;
	if(c==0&&n==0&&m==0&&s==0&&d==0) break;
	memset(rosen,-1,sizeof(rosen));
	REP(i,m){
	    int a,b,f;
	    cin >> a >> b >> f;
	    rosen[a][b] = f;
	    rosen[b][a] = f;
	}
	vector<bool>  used(n+1,false);
	vector<int> nanika;
	used[s] = true;
	cout << saiki(s, nanika ,used) << endl;
    }
    return 0;
}