#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int maxn = 105;
vector<pair<int, int>> graph[maxn];
int dist[maxn][10][500];
struct node {
    int idx, shortest_distance, k_left, path_with_automation;
    node () {}
    node(int _idx, int _shortest_distance, int _k_left, int _path_with_automation) {
        idx = _idx;
        shortest_distance = _shortest_distance;
        k_left = _k_left;
        path_with_automation = _path_with_automation;
    }
    
    bool operator < (const node & tmp) const {
        return shortest_distance > tmp.shortest_distance;
    }
    
};
int main() {
    int n, x;
    cin >> n >> x;
    int K, L;
    cin >> K >> L;
    
    int m;
    cin >> m;
    
    for(int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        graph[a].push_back(make_pair(b, c));
        graph[b].push_back(make_pair(a, c));
    }
    
    for(int i = 0; i <= n; i++) {
        for(int j = 0; j <= K; j++) {
            for(int k = 0; k <= L; k++) {
                dist[i][j][k] = 2e9;
            }
        }
    }
    
    priority_queue<node> pq;
    pq.push(node(1, 0, K, L));
    dist[1][0][0] = 0;
    
    while(!pq.empty()) {
        node c = pq.top();
        pq.pop();
        
        int new_path = c.path_with_automation;
        if(c.idx <= x and new_path > 0) {
            new_path = 0;
        }
        if(new_path > 0) {
            for(int i = 0; i < (int) graph[c.idx].size(); i++) {
                int neighbour = graph[c.idx][i].first;
                int weight = graph[c.idx][i].second;
                if(new_path - weight >= 0 and c.shortest_distance < dist[neighbour][c.k_left][new_path - weight]) {
                    dist[neighbour][c.k_left][new_path - weight] = c.shortest_distance;
                    pq.push(node(neighbour, c.shortest_distance, c.k_left, new_path - weight));
                }
            }
            new_path = 0;
        }
        
        for(int i = 0; i < (int) graph[c.idx].size(); i++) {
            int neighbour = graph[c.idx][i].first;
            int weight = graph[c.idx][i].second;
            if(c.shortest_distance + weight < dist[neighbour][c.k_left][new_path]) {
                dist[neighbour][c.k_left][new_path] = c.shortest_distance + weight;
                pq.push(node(neighbour, c.shortest_distance + weight, c.k_left, new_path));
            }
        }
        
        if(c.k_left > 0) {
            new_path = L;
            for(int i = 0; i < (int) graph[c.idx].size(); i++) {
                int neighbour = graph[c.idx][i].first;
                int weight = graph[c.idx][i].second;
                
                if(new_path - weight >= 0 and c.shortest_distance < dist[neighbour][c.k_left - 1][new_path - weight]) {
                    dist[neighbour][c.k_left - 1][new_path - weight] = c.shortest_distance;
                    pq.push(node(neighbour, c.shortest_distance, c.k_left - 1, new_path - weight));
                }
            }
        }
        
    }
    int result = 2e9;
    
    for(int i = 0; i <= K; i++) {
        for(int j = 0; j <= L; j++) {
            result = min(result, dist[n][i][j]);
        }
    }
    cout << result << endl;
    
    return 0;
}