#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <queue>
#include <cstring>using namespace std;const int M = 2e6 + 5e5 + 10;#define gc getchar()
inline int read() {int x = 0, f = 1; char c = gc;while(c < '0' || c > '9') {if(c == '-') f = -1; c = gc;}while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = gc;return x * f;
}int dis[M], head[M], cnt, vis[M];
struct Node {int u, v, nxt, w;
} G[M];struct Node1 {int u, dis;bool operator < (const Node1 a) const {return this->dis > a.dis;}
};priority_queue <Node1> Q;int n, m, k;
int s, t;void Link(int u, int v, int w) {G[++ cnt].v = v; G[cnt].u = u; G[cnt].w = w; G[cnt].nxt = head[u]; head[u] = cnt;
}void Dijkstra() {memset(dis, 0x3f, sizeof dis);Q.push((Node1){s, 0});dis[s] = 0;while(!Q.empty()) {Node1 tp = Q.top();Q.pop();if(vis[tp.u]) continue;vis[tp.u] = 1;for(int i = head[tp.u]; ~ i; i = G[i].nxt) {int v = G[i].v;if(dis[v] > dis[tp.u] + G[i].w) {dis[v] = dis[tp.u] + G[i].w;Q.push((Node1) {v, dis[v]});}}}
}int main() {n = read(), m = read(), k = read();for(int i = 1; i <= n * k + n; i ++) head[i] = -1;s = read() + 1, t = read() + 1;for(int i = 1; i <= m; i ++) {int u = read() + 1, v = read() + 1, w = read();for(int j = 0; j < k; j ++) {Link(j * n + u, j * n + v, w);Link(j * n + v, j * n + u, w);Link(j * n + u, (j + 1) * n + v, 0);Link(j * n + v, (j + 1) * n + u, 0);}Link(n * k + u, n * k + v, w);Link(n * k + v, n * k + u, w);}Dijkstra();int Ans = (1 << 30);for(int i = 0; i <= k; i ++) {Ans = min(Ans, dis[i * n + t]);}cout << Ans;return 0;
}