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 <algorithm>
#include <cstring>
#include <utility>
#include <vector>
#include <functional>

#define MAX 1000000000
#define Debug(X) debug( __LINE__, X )

typedef std::pair<int, int> p;

int c, n, m, s, d;
int route[101][101];
int cost[101];
std::vector<std::vector<int> > visited(101);
bool used[101];

template<class T>
void debug( int line, T dbg ){
	std::cout << line << ": " << dbg << std::endl;
}

int main(){
	while( std::cin >> c >> n >> m >> s >> d, c * n * m * s * d ){
		for( int i = 0; i < 101 * 101; ++i )
			route[i / 101][i % 101] = MAX;
		for( int i = 0; i < 101; ++i )
			cost[i] = MAX;

		memset( used, 0, sizeof( used ) );
		visited.clear();

		unsigned int tmp[3];
		while( m-- ){
			int cnt = 3;
			while( cnt-- ) std::cin >> tmp[2 - cnt];

			route[tmp[0]][tmp[1]] = tmp[2];
			route[tmp[1]][tmp[0]] = tmp[2];
		}

		cost[s] = 0;
		
		while( true ){
			unsigned pos = 0;
			for( int i = 1; i <= n; ++i ){
				if( !used[i] && (pos == 0 || cost[pos] > cost[i]) ) pos = i;
			}
			
			used[pos] = 1;
			if( pos == 0 ) break;
					
			for( int i = 1; i <= n; ++i ){
				if( i != pos ){
					std::vector<int> tmpv;
					tmpv = visited[pos];
					tmpv.push_back( route[pos][i] );
					std::sort( tmpv.begin(), tmpv.end(), std::greater<int>() );
					
					int cnt = 0;
					for( int l = 0; l < tmpv.size(); ++l ){
						if( l < c ) cnt += tmpv[l] / 2;
						else cnt += tmpv[l];
					}
					if( cnt < cost[i] ){
						cost[i] = cnt;
						visited[i] = tmpv;
					}
					
				}
			}
		}

		std::cout << cost[d] << std::endl;
	}

	return 0;
}

C++: #include<iostream>
#include<queue>
#include<map>
#define MAX 10000000
#include<vector>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
struct edge{
	int cost,to;
};
typedef pair<int,int> p;
typedef pair<int,p> P;
//`Pbg@»ÝÌ@v
int main(){
	int tic,n,m,s,a,b,g,d[11][101],f;
	//d ticket place
	while(cin>>tic>>n>>m>>s>>g,tic||n||m||s||g){
		s--;g--;
		//tic `Pbg
		//n Ì
		//m ´Ì
		//s¨g
		vector<edge> v[101];
		rep(i,m){
			cin>>a>>b>>f;
			a--;b--;
			edge c;
			c.cost=f;
			c.to=b;v[a].push_back(c);
			c.to=a;v[b].push_back(c);
		}
		rep(i,tic+1)
		rep(j,n){
			if(j==s)
			d[i][j]=0;
			else
			d[i][j]=MAX;
		}
		int nowticket,nowplace,nowsum;
		priority_queue<P,vector<P>,greater<P> > que;
		P now;
		que.push(P(tic,p(s,0)));
		while(!que.empty()){
			now=que.top();
			que.pop();
			nowticket=now.first;
			nowplace=now.second.first;
			nowsum=now.second.second;
			if(d[nowticket][nowplace]<nowsum)
				continue;
			rep(i,(int)v[nowplace].size()){
				edge e=v[nowplace][i];
				if(nowticket>0){
					if(d[nowticket-1][e.to]>e.cost/2+nowsum){
						d[nowticket-1][e.to]=e.cost/2+nowsum;
						que.push(P(nowticket-1,p(e.to,d[nowticket-1][e.to])));
					}
				}
				if(d[nowticket][e.to]>e.cost+nowsum){
						d[nowticket][e.to]=e.cost+nowsum;
						que.push(P(nowticket,p(e.to,d[nowticket][e.to])));
				}
			}
		}
		int mi=100000000;
		rep(i,tic+1)
		mi=min(mi,d[i][g]);
		cout<<mi<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <queue>

#define INF 1e9

using namespace std;

struct Edge {
	int to, cost;
};
struct Node {
	int now, rest, cost;
};
bool operator <(const Node& n1, const Node& n2) {
	return n1.cost < n2.cost;
}

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

		vector<Edge> m[100];
		for (int i = 0; i < l; ++i) {
			int a, b, f; cin >> a >> b >> f; --a, --b;
			m[a].push_back( (Edge){ b, f } );
			m[b].push_back( (Edge){ a, f } );
		}

		int ans[100][11]; fill(&ans[0][0], &ans[0][0]+100*11, INF);
		priority_queue<Node> Q; Q.push( (Node){s, c, 0} );
		while ( !Q.empty() ) {
			Node node = Q.top(); Q.pop();
			if (node.cost >= ans[node.now][node.rest]) continue;
			ans[node.now][node.rest] = node.cost;

			for (int i = 0; i < m[node.now].size(); ++i) {
				Edge& e = m[node.now][i];
				if (node.cost+e.cost < ans[e.to][node.rest]) {
					Q.push( (Node){ e.to, node.rest, node.cost+e.cost } );
				}

				if (node.rest > 0) {
					if (node.cost+e.cost/2 < ans[e.to][node.rest-1]) {
						Q.push( (Node){ e.to, node.rest-1, node.cost+e.cost/2 } );
					}
				}
			}
		}
		int a = INF;
		for (int i = 0; i <= c; ++i) a = min(a, ans[d][i]);
		cout << a << endl;
	}
}