Go: package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"
)

var scanner = bufio.NewScanner(os.Stdin)

const INF = 0x7FFFFFFF

var pass [][]int

func main() {
	for scanner.Scan() {
		pass = make([][]int, 200)
		for i := range pass {
			pass[i] = make([]int, 200)
		}
		buf := strings.Split(scanner.Text(), " ")
		c, _ := strconv.Atoi(buf[0])
		n, _ := strconv.Atoi(buf[1])
		m, _ := strconv.Atoi(buf[2])
		s, _ := strconv.Atoi(buf[3])
		d, _ := strconv.Atoi(buf[4])
		if c == 0 && n == 0 && m == 0 && s == 0 && d == 0 {
			break
		}
		s--
		d--
		for i := 0; i < 200; i++ {
			for j := 0; j < 200; j++ {
				pass[i][j] = INF
			}
		}
		for i := 0; i < 200; i++ {
			pass[i][i] = 0
		}
		for i := 0; i < m; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			a, _ := strconv.Atoi(buf_[0])
			b, _ := strconv.Atoi(buf_[1])
			f, _ := strconv.Atoi(buf_[2])
			a--
			b--
			pass[a][b] = f
			pass[b][a] = f
		}
		fmt.Println(dijkstra(s, d, c, n))
	}
}

func dijkstra(s, g, c, n int) float64 {
	d := make([][]float64, 200)
	used := make([][]bool, 200)
	for i := 0; i < 200; i++ {
		d[i] = make([]float64, 20)
		used[i] = make([]bool, 20)
	}
	for i := range d {
		for j := range d[i] {
			d[i][j] = INF
		}
	}
	d[s][c] = 0
	for {
		v := -1
		w := -1
		for u := 0; u < n; u++ {
			for i := 0; i < c+1; i++ {
				if !used[u][i] && (v == -1 || d[u][i] < d[v][w]) {
					v = u
					w = i
				}
			}
		}
		if v == -1 {
			break
		}
		used[v][w] = true
		for u := 0; u < n; u++ {
			d[u][w] = math.Min(d[u][w], d[v][w]+float64(pass[v][u]))
			if w-1 >= 0 && pass[v][u] != INF {
				d[u][w-1] = math.Min(d[u][w-1], d[v][w]+(float64(pass[v][u]/2.0)))
			}
		}
	}
	ret := float64(INF)
	for i := 0; i < c+1; i++ {
		ret = math.Min(ret, d[g][i])
	}
	return ret
}

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 dp[101];
int saiki(int p,vector<int> st,vector<bool> &u){
    if(dp[p]>0) return dp[p];
    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 dp[p] = ans;
}

int main(){
    while(true){
	scanf("%d%d%d%d%d",&c,&n,&m,&s,&d);
	if(c==0||n==0||m==0||s==0||d==0) break;
	memset(rosen,-1,sizeof(rosen));
	memset(dp,-1,sizeof(dp));
	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;
}

C++: #include <stdio.h>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
typedef long long int ll;

using namespace std;

int minimum,num_ticket,num_town,m,start,goal,costTable[101][101];


struct Info{
    Info(){
        for(int i = 1; i <= num_town; i++){
            visited[i] = false;
        }
        current_town = 0;
        index = 0;
    }
    bool visited[102];
    int current_town,index,costs[102],visited_town[101];

};

void func(Info info){

    int sum = 0,limit;

    if(info.current_town == goal || minimum != 2000000000)
    {

    	limit = min(num_ticket,info.index);

    	for(int i = 0; i < limit; i++){
    		sum += info.costs[i]/2;
    	}

    	for(int i = limit; i < info.index; i++){
    		sum += info.costs[i];
    	}

		if(info.current_town == goal){
			minimum = min(minimum,sum);
			return;
		}else{
			if(sum >= minimum){
				return;
			}
		}

    }

    int calc;
    for(int i = 1; i <= num_town; i++){
        if(costTable[info.current_town][i] != -1 && info.visited[i] == false){
            Info new_info;
            for(int k = 0; k < info.index; k++){
            	new_info.visited[info.visited_town[k]] = true;
            	new_info.visited_town[k] = info.visited_town[k];
            }
            new_info.visited[i] = true;
            new_info.visited_town[info.index] = i;
            new_info.current_town = i;

            if(costTable[info.current_town][i] > info.costs[0]){
            	new_info.costs[0] = costTable[info.current_town][i];
            	for(int k = 1; k <= info.index; k++){
            		new_info.costs[k] = info.costs[k-1];
            	}
            }else if(costTable[info.current_town][i] <= info.costs[info.index-1]){
            	for(int k = 0; k < info.index; k++){
            		new_info.costs[k] = info.costs[k];
            	}
            	new_info.costs[info.index] = costTable[info.current_town][i];
            }else{
            	for(calc = 0; info.costs[calc] >= costTable[info.current_town][i];calc++)new_info.costs[calc] = info.costs[calc];
				new_info.costs[calc] = costTable[info.current_town][i];
				calc++;
				for(;calc-1 < info.index;calc++)new_info.costs[calc] = info.costs[calc-1];
            }
            new_info.index = info.index+1;
            func(new_info);

        }
    }
}

int main(){

    int from,to,fee;

    while(true){
        scanf("%d %d %d %d %d",&num_ticket,&num_town,&m,&start,&goal);
        if(num_ticket == 0 && num_town == 0 && m == 0 && start == 0 && goal == 0)break;

        minimum = 2000000000;

        for(int i = 1; i <= num_town; i++){
            for(int k = 1; k <= num_town; k++)costTable[i][k] = -1;
        }

        for(int i = 0; i < m; i++){
            scanf("%d %d %d",&from,&to,&fee);
            costTable[from][to] = fee;
            costTable[to][from] = fee;
        }

        Info info;

        info.current_town = start;
        info.visited[start] = true;

        func(info);

        printf("%d\n",minimum);
    }


    return 0;
}