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 <iostream>
#include <array>

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;
};

array<edge,500> 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){
        rep(i,m) cin>>E[i].from>>E[i].to>>E[i].cost;
        rep(i,c+1){
            dp[i].fill(10000000);
            dp[i][s]=0;
            bool end;
            while(1){
                end=1;
                rep(j,m){
                    edge& e=E[j];
                    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 <cstdio>
#include <cstring>
#include <iostream>
#include <queue>

using namespace std;

struct Node
{
	int num, cost, ticket;
	Node(int n, int c, int t)
	{
		num = n;cost = c; ticket = t;
	}

	bool operator < (const Node &o) const
	{
		return cost > o.cost;
	}
};

const int MAX_NODE_ID = 1024;
const int MAX_TICKET = 1024;
bool visited[MAX_NODE_ID][MAX_TICKET];

int c, n, m, s, d;

#define MAX 50000
int map[101][101];

int main()
{
	while (true)
	{
		cin >> c >> n >> m >> s >> d;
		if (c == 0 && n == 0 && m == 0 && s == 0 && d == 0) break;
		for (int i = 1; i <= n; i++)
			for (int j = 1; j <= n; j++)
				map[i][j] = MAX;
		for (int i = 0; i < m; i++)
		{
			int a, b, f;
			cin >> a >> b >> f;
			map[a][b] = map[b][a] = f;
		}
		for (int i = 0; i < MAX_NODE_ID; i++)
			for (int j = 0; j < MAX_TICKET; j++)
				visited[i][j] = false;
		priority_queue<Node> que;
		int minimum = MAX;
		que.push(Node(s, 0, c));
		while (!que.empty())
		{
			Node nod = que.top();
			que.pop();
			if (nod.num == d)
			{
				//S[
				minimum = min<int>(minimum, nod.cost);
			}
			else
			{
				for (int i = 1; i <= n; i++)
				{
					if (map[nod.num][i] < MAX && !visited[nod.num][nod.ticket])
					{
						que.push(Node(i, nod.cost + map[nod.num][i], nod.ticket));
						if (nod.ticket > 0)
						{
							que.push(Node(i, nod.cost + map[nod.num][i] / 2, nod.ticket - 1));
						}
					}
				}
			}
			visited[nod.num][nod.ticket] = true;
		}
		cout <<	minimum << endl;
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<queue>
#include<vector>
#define REP(i,s,n) for(int i=s;i<n;i++)
#define rep(i,n) REP(i,0,n)
#define F first
#define S second
using namespace std;
typedef pair<int,int> P;// F -> to, S -> cost
typedef pair<P,int> PP;// F->P(to,cost), S->discount
int c,n,m,s,d;
vector<PP> vec[1000];
int MD[1000][13];
const int INF = 1<<29;

void dijkstra(){
  priority_queue<PP,vector<PP>,greater<PP> > que;
  rep(i,n+1)rep(j,13)MD[i][j] = INF;
  //syokika
  MD[s][c] = 0;
  que.push(PP(P(0,s),c));//dis,start,discount

  while(!que.empty() ){
    PP p = que.top();que.pop(); //priority_queのPPと
    int v = p.F.S;
    
    for(int i=0;i<vec[v].size();i++){
      PP po = vec[v][i]; //vectorのPPは意味が違うので注意！！！
      //if(MD[v][po.S] < po.F.S)continue;
      if(MD[po.F.F][c] > MD[v][c] + po.F.S){
	MD[po.F.F][c] = MD[v][c]+po.F.S;
	que.push(PP(P(MD[po.F.F][c],po.F.F),c));
      }
      if(po.S > 0 && MD[po.F.F][p.S-1] > MD[v][p.S] + po.F.S/2 ){
	MD[po.F.F][p.S-1] = MD[v][p.S]+po.F.S/2;
	que.push(PP(P(MD[po.F.F][p.S-1],po.F.F),p.S-1));
	vec[v][i].S--;
      }
    }
  }
}


int main(){
  int x,y,co;
  while(true){
    cin >> c >> n >> m >> s >> d;
    if(c+n+m+s+d == 0)break;
    rep(i,1000)vec[i].clear();
    rep(i,m){
      cin >> x >> y >> co;
      vec[x].push_back(PP(P(y,co),c));
      vec[y].push_back(PP(P(x,co),c));
    }
    dijkstra();
    int ans = INF;
    for(int i=0;i<=c;i++){
      ans = min(ans,MD[d][i]);
    }
    cout << ans << 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 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));
	REP(i,m){
	    int a,b,f;
	    cin >> a >> b >> f;
	    rosen[a][b] = f;
	    rosen[b][a] = f;
	}
	int ans = 100000000;
	vector<bool>  used(n+1,false);
	vector<int> nanika;
	used[s] = true;
	queue<int> q;
        queue<string> st;
	vector<bool> u(n+1,false);
	u[s] = true;
	q.push(s);
	st.push(to_string(s));
	while(!q.empty()){
	    int p = q.front();
            string ss = st.front();
	    q.pop();
	    st.pop();
	    if(p == d){
		vector<int> v;
		int x = -1;
		int pre = s;
		REP(i,ss.size()){
		    if(ss[i]==' '){
			int var = stoi(ss.substr(x+1,i-1-x));
			v.PB(rosen[pre][var]);
			pre = var;
			x = i;
		    }
		}
		v.PB(rosen[pre][stoi(ss.substr(x+1,ss.size()-x-1))]);
		int sum = 0;
		int tc = min((int)(v.size()),c);
		sort(RALL(v));
		REP(i,tc){
		    v[i] /= 2;
		}
		REP(i,v.size()) sum += v[i];
		ans = min(ans,sum+1);
		continue;
	    }
	    FOR(i,1,n+1){
		if(rosen[p][i]>0 && !u[i]){
		    if(i!=d)
			u[i] = true;
		    q.push(i);
		    string temps = ss;
		    temps += " " + to_string(i);
		    st.push(temps);
		}
	    }
	}
	cout << ans << endl;
    }
    return 0;
}