#include<iostream>
#include<cstring>
#include<queue>

using namespace std;
const int N = 1e4 + 10, M = 1e5 + 10;
typedef pair<int, int> PII;
int h[N], e[M], ne[M], w[M], idx;
int n, m, k;
int s, tar;
bool st[N];
long long dist[11][N];

void add(int a, int b, int c){
    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx ++;
}

void dijkstra(int u)
{
    priority_queue<PII, vector<PII>, greater<PII>> heap;
    dist[u][s] = 0;
    heap.push({0, s});
    for (int i = 0; i < n - 1; i ++ )
    {
        auto ver = heap.top();
        heap.pop();
        int t = ver.second;
        for(int j = h[t]; ~j; j = ne[j]){
            int k = e[j];
            if(u == 0){
                if(dist[u][t] + w[j] < dist[u][k]){
                    dist[u][k] = dist[u][t] + w[j];
                    heap.push({dist[u][k], k});
                }
            } 
            else{
                if(dist[u][k] > min(dist[u - 1][t], dist[u][t] + w[j])){
                    dist[u][k] = min(dist[u - 1][t], dist[u][t] + w[j]);
                    heap.push({dist[u][k], k});
                }
                
            } 
        }
    }
}

int main(){
    cin >> n >> m >> k;
    cin >> s >> tar;
    memset(h, -1, sizeof h);
    while(m --){
        int a, b, c;
        cin >> a >> b >> c;
        add(a, b, c), add(b, a, c);
    }
    memset(dist, 0x3f, sizeof dist);
    for(int i = 0; i <= k; i ++){
        dijkstra(i);
    }
    
    cout << dist[k][tar];
    return 0;
}