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 <iostream>
#include <queue>
#include <vector>
#include <algorithm>
#include <functional>

using namespace std;

#define INF 1000000000
#define MAX_N 100

class CDij{
public:
	int min_c;
	vector<int> vec;
};

int n;
int c,m;
int s,d;

queue<int> q;

int cost[MAX_N+1][MAX_N+1];

CDij dp[MAX_N+1];//sからiに行くまでの最小運賃

int main(){

	while(1){
		cin >> c >> n >> m >> s >> d;

		if(c+n+m+s+d==0) break;

		for(int i=0;i<=n;i++){
			for(int j=0;j<=n;j++){
				cost[i][j] = -1;
			}
		}

		for(int i=1;i<=n;i++){
			dp[i].min_c = INF;
			for(int j=0;j<dp[i].vec.size();j++){
				dp[i].vec.pop_back();
			}
		}

		for(int i=0;i<m;i++){
			int a,b,p;
			cin >> a >> b >>p;
			cost[a][b] = p;
			cost[b][a] = p;
		}

		q.push(s);
		dp[s].min_c = 0;
		dp[s].vec.push_back(s);

		while(!q.empty()){
			int now = q.front();
			q.pop();

			for(int i=1;i<=n;i++){
				if(cost[now][i] != -1){
					vector<int> root;
					root = dp[now].vec;
					root.push_back(i);

					vector<int> vec;

					int size = root.size()-1;

					for(int j=0;j<size;j++){
						vec.push_back( cost[root[j]][root[j+1]] );
					}
					sort(vec.begin(),vec.end(),greater<int>());

					size = vec.size();
					for(int j=0;j<min(c,size);j++){
						vec[j] /= 2;
					}

					int sum = 0;
					size = vec.size();

					for(int j=0;j<size;j++){
						sum+=vec[j];
					}

					if(sum < dp[i].min_c){
						dp[i].min_c = sum;
						dp[i].vec = root;
						q.push(i);
					}
				}
			}
	
		}

		cout << dp[d].min_c << endl;

	}
	return 0;
}

C++: #include <iostream>
#include <array>
#include <vector>

using namespace std;
#define loop(i,a,b) for(int i=(a); i<(int)(b); i++)
#define rep(i,b) loop(i,0,b)
#define eacha(e,c) for(auto &e:c)

struct edge {
    int from,to,cost;
};

vector<edge> E;
array<array<int,11>,101> dp;
int c,n,m,s,d;

int main(){
    while(cin>>c>>n>>m>>s>>d, c|n|m|s|d){
        vector<edge>(m).swap(E);
        rep(i,m) cin>>E[i].from>>E[i].to>>E[i].cost;
        rep(i,c+1){
            dp[i].fill(1<<30);
            dp[i][s]=0;
            bool end;
            while(1){
                end=1;
                eacha(e,E){
                    rep(dir,2){
                        int nd=dp[i][e.from]+e.cost;
                        if(i!=0) nd=min(dp[i-1][e.from]+e.cost/2,nd);
                        if(nd<dp[i][e.to]) dp[i][e.to]=nd,end=false;
                        swap(e.to,e.from);
                    }
                }
                if(end) break;
            }
        }
        cout<<dp[c][d]<<endl;
    }
}

C++: #include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
#include <utility>
#include <functional>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <deque>
 
using namespace std;
 
#define rep(i,n) REP(i,0,n)
#define REP(i,s,e) for(int i=(s); i<(int)(e); i++)
#define pb push_back
#define mp make_pair
#define all(r) r.begin(),r.end()
#define fi first
#define se second
#define println(X) cout<<X<<endl;
#define DBG(X) cout<<#X<<" : "<<X<<endl;
 
 
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef vector<ll> vl;
typedef vector<vl> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> pp;

const int INF = 1e9;

double EPS = 1e-10;


int c, n, m, s, g;



const int MAX_V = 510;

int d[MAX_V][MAX_V][15];
int connect[MAX_V][MAX_V];
int V;
 
void warshall_floyd_init(){
	for(int i = 0; i < V; i++){
		for(int j = 0; j < V; j++){
			for(int k = 0; k <= c; k++){
				if(i == j) d[i][i][k] = 0;
				else d[i][j][k] = INF;
			}
			connect[i][j] = 0;
		}
	}
}

void warshall_floyd() {
				for(int l = c; l>=0; l--){
				//for(int l = 0; l <= c; l++){
	for (int k = 0; k < V; k++) {
		for (int i = 0; i < V; i++) {
			for (int j = 0; j < V; j++) {
					d[i][j][l] = min({d[i][j][l], d[i][k][l] + d[k][j][c], d[i][k][c] + d[k][j][l]});
					if(l>0 && connect[k][j] > 0){
						d[i][j][l-1]=min(d[i][j][l-1], d[i][k][l]+connect[k][j]/2);
					}
					if(l>0 && connect[i][k] > 0){
						d[i][j][l-1]=min(d[i][j][l-1],connect[i][k]/2 + d[k][j][l]);						
					}
				}
			}
		}
	}
}
int main(){
	int a, b, f;
	int ans;
	while(cin>>c>>n>>m>>s>>g){
		if(c == 0 && n == 0 && m == 0 && s == 0 && g == 0) break;
		s--; g--;
		V = n;
		warshall_floyd_init();
		//cout<<d[0][2][0]<<endl;
		for(int i = 0; i < m; i++){
			cin>>a>>b>>f;
			//f/=10;
			a--; b--;
			//d[a][b][c] = d[b][a][c] = f;
			d[a][b][c] = min(d[a][b][c], f);
			d[b][a][c] = min(d[b][a][c], f);
			connect[a][b] = connect[b][a] = f;	
		}
		warshall_floyd();
		int ans = INF;
		for(int i = 0; i <= c; i++) ans = min(ans, d[s][g][i]);
		cout<<ans<<endl;
		//cout<<" "<<d[4][5][2]<<endl;
	}
	
}