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 <queue>
#include <cstring>
using namespace std;

class State{
public:
  int id, rem, cost;

  State(int _id, int _rem, int _cost){
    id = _id;
    rem = _rem;
    cost = _cost;
  }

  bool operator<(const State &st)const{
    return cost > st.cost;
  }
};

int c, n, m, s, d;
bool closed[102][12];
int t[102][102];

void solve(){
  priority_queue<State> open;
  memset(closed, 0, sizeof(closed));
  open.push(State(s, c, 0));

  while(!open.empty()){
    State st = open.top(); open.pop();
    if(closed[st.id][st.rem]) continue;
    closed[st.id][st.rem] = true;

    if(st.id == d){
      cout << st.cost << endl;
      return;
    }

    for(int i = 0; i < n; i++){
      if(t[st.id][i] != -1){
        open.push(State(i, st.rem, st.cost + t[st.id][i]));
        if(st.rem > 0){
          open.push(State(i, st.rem - 1, st.cost + t[st.id][i] / 2));
        }
      }
    }
  }
}

int main(){
  while(cin >> c >> n >> m >> s >> d, c || n || m || s || d){
    s--;
    d--;

    memset(t, -1, sizeof(t));

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

    solve();
  }
}

C++: #include<iostream>
#include<utility>
#include<vector>
#include<cstdio>
#include<queue>
#include <map>
using namespace std;
typedef pair<int, int> P;
typedef pair<int, P> PP;
//int in(){int x;cin>>x;return x;}

int main ()
{
	int c,n,m,s,d;
	while(cin>>c>>n>>m>>s>>d&&c&&n&&m&&s&&d)
	{
		int flg[110]={};
		int ans =0;
		priority_queue < PP, vector<PP>, greater<PP> > q;
		vector< pair< int,int > > way[110];
		for(int i=0;i<m;i++)
		{
			int a,b,f;
			cin>>a>>b>>f;
			way[a].push_back(pair<int,int>(b,f));
			way[b].push_back(pair<int,int>(a,f));
		}
		pair< int , pair<int,int> > next;
		next.first=0;next.second.first=s;next.second.second=c;
		q.push(next);
		while(!q.empty())
		{
			pair< int , pair<int,int> > now=q.top();q.pop();
			flg[now.second.first]=0;
			if(now.second.first==d)
			{
				ans=now.first;
				break;
			}
			
			for(int i=0;i<way[now.second.first].size();i++)
			{
				if(flg[way[now.second.first][i].first]==1)continue;
				next.first=now.first+way[now.second.first][i].second;
				next.second.first=way[now.second.first][i].first;
				q.push(next);
				next.first=now.first+way[now.second.first][i].second/2;
				next.second.first=way[now.second.first][i].first;
				next.second.second=now.second.second-1;
				q.push(next);
			}
			
		}
		cout<<ans<<endl;
	}
	
	
	return 0;
}

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);
						//printf(" %d (%d -> %d -> %d), %d %d\n", l, i, k, j, d[i][j][l-1], d[i][k][l]+connect[k][j]/2);
					}
				}
			}
		}
	}
}
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;
	}
	
}