#include <bits/stdc++.h>

using namespace std;

#define endl "\n"

typedef pair<int, int> pii;

const int N = 4e6 + 10, M = 2e5 + 10, inf = 0x3f3f3f3f;

int e[N], ne[N], h[M], w[N], idx;
priority_queue<pii, vector<pii>, greater<pii>> hp;
int d[M];
bool vis[M];

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

void dijk(int x)
{
    memset(d, 0x3f, sizeof d);
    d[x] = 0;
    hp.push({0, x});
    while (!hp.empty())
    {
        auto t = hp.top();
        hp.pop();
        if (vis[t.second])
            continue;
        vis[t.second] = true;
        for (int i = h[t.second]; i != -1; i = ne[i])
        {
            int j = e[i];
            if (d[j] > d[t.second] + w[i])
            {
                d[j] = d[t.second] + w[i];
                hp.push({d[j], j});
            }
        }
    }
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
    memset(h, -1, sizeof h);
    int n, m, k;
    cin >> n >> m >> k;
    int s, t;
    cin >> s >> t;
    for (int i = 0; i < m; i++)
    {
        int a, b, c;
        cin >> a >> b >> c;
        add(a, b, c), add(b, a, c);
        for (int j = 1; j <= k; j++)
        {
            add(a + j * n, b + j * n, c), add(b + j * n, a + j * n, c);
            add(a + (j - 1) * n, b + j * n, 0), (b + (j - 1) * n, a + j * n, 0);
        }
    }
    dijk(s);
    int ans = d[t];
    for (int i = 1; i <= k; i++)
        ans = min(ans, d[t + i * n]);
    cout << ans << endl;
    return 0;
}