// AOJ 1318 Long Distance Taxi
// 2018.3.2 bal4u
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
// Hash table for string
#define HASHSIZ   35023
typedef struct { char *s; short id; } HASH;
HASH hash[HASHSIZ+2], *hashend = hash+HASHSIZ;
 
int insert(char *s, int id)
{
    unsigned long long i;
    char *p;
    HASH *tp;
 
    i = 0, p = s; while (*p) i = (i<<6) + *p++;
    tp = hash + (int)(i % HASHSIZ);
    while (tp->s != NULL) {
        if (!strcmp(tp->s, s)) return tp->id;
        if (++tp == hashend) tp = hash;
    }
    tp->s = s, tp->id = id;
    return -1;
}
 
#define QMAX 6002
typedef struct { int t; short s, c; } QUE;
QUE que[QMAX]; int qsize;
 
#define PARENT(i) ((i)>>1)
#define LEFT(i)   ((i)<<1)
#define RIGHT(i)  (((i)<<1)+1)
 
void min_heapify(int i)
{
    int l, r, min;
    QUE qt;
 
    l = LEFT(i), r = RIGHT(i);
    if (l < qsize && que[l].t < que[i].t) min = l; else min = i;
    if (r < qsize && que[r].t < que[min].t) min = r;
    if (min != i) {
        qt = que[i], que[i] = que[min], que[min] = qt;
        min_heapify(min);
    }
}
 
void deq()
{
    que[0] = que[--qsize];
    min_heapify(0);
}

void enq(short s, int t, short c)
{
    int i, min;
    QUE qt;
 
    i = qsize++;
    que[i].s = s, que[i].t = t, que[i].c = c;
    while (i > 0 && que[min = PARENT(i)].t > que[i].t) {
        qt = que[i], que[i] = que[min], que[min] = qt;
        i = min;
    }
}
 
//#define getchar_unlocked()  getchar()
int in()
{
    int n = 0;
    int c = getchar_unlocked();
    do n = 10*n + (c & 0xf), c = getchar_unlocked();
    while (c >= '0');
    return n;
}
 
void ins(char *buf)
{
    while ((*buf = getchar_unlocked()) > ' ') buf++;
    *buf = 0;
}
 
#define MAX 6002
short memo[3002*3];
short hi[MAX], *to[MAX], *dd[MAX];
char city[MAX][17]; int sz;
char LPG[MAX];
char mk[MAX][2002];
 
int dijkstra(int n, int cap, int start, int goal)
{
    int i, s, e, c, nc, d;
 
    memset(mk, 0, sizeof(mk));
    qsize = 0;
    enq(start, 0, cap); mk[start][cap] = 1;
    while (qsize) {
        s = que[0].s, d = que[0].t, c = que[0].c, deq();
        if (s == goal) return d;
 
        if (LPG[s]) c = cap;
		memset(mk[s], 1, c);

        for (i = 0; i < hi[s]; i++) {
			if ((nc = c - dd[s][i]) < 0) continue;
            e = to[s][i];
            if (mk[e][nc]) continue;
			mk[e][nc] = 1, enq(e, d+dd[s][i], nc);
        }
    }
    return -1;
}
 
int main()
{
    int N, M, cap, i, j, a, b, c;
    char buf[20];
 
    while (N = in()) {
        for (a = 0; a < sz; a++) {
            if (hi[a]) free(to[a]), free(dd[a]);
        }
 
        M = in(), cap = 10*in();
        memset(hash, 0, sizeof(hash));
 
        ins(city[0]), ins(city[1]);
        insert(city[0], 0), insert(city[1], 1);
 
        memset(hi, 0, sizeof(hi));
        sz = 2;
        j = 0, i = N; while (i--) {
			ins(city[sz]), a = insert(city[sz], sz);
            if (a < 0) a = sz++;
            memo[j++] = a, hi[a]++;
            ins(city[sz]), b = insert(city[sz], sz);
            if (b < 0) b = sz++;
            memo[j++] = b, hi[b]++;
            memo[j++] = in();
        }
        for (a = 0; a < sz; a++) if (hi[a]) {
            to[a] = malloc(hi[a] << 1);
            dd[a] = malloc(hi[a] << 1);
        }
        memset(hi, 0, sz << 1);
        j = 0; while (N--) {
            a = memo[j++], b = memo[j++], c = memo[j++];
            i = hi[a]++, to[a][i] = b, dd[a][i] = c;
            i = hi[b]++, to[b][i] = a, dd[b][i] = c;
        }
        memset(LPG, 0, sz);
        for (i = 0; i < M; i++) {
            ins(buf), a = insert(buf, -1);
            if (a >= 0) LPG[a] = 1;
        }
 
        printf("%d\n", dijkstra(sz, cap, 1, 0));
    }
    return 0;
}
