#include <cstdio>
#include <cstring>const int des = 1000000001;int T, n, lj, x[30], y[30], TT, tx1, ty1, tx2, ty2, lasty, idx;
int que[60], head_, tail, h, stp[60];
struct graph {int head[60], to[3600], next[3600], lb;void clear(void) {memset(head, -1, sizeof head);memset(next, -1, sizeof next);lb = 0;}void ist(int aa, int ss) {to[lb] = ss;next[lb] = head[aa];head[aa] = lb;++lb;}
} g;int main(void) {freopen("jumping.in", "r", stdin);freopen("jumping.out", "w", stdout);scanf("%d", &TT);while (TT--) {memset(x, 0, sizeof x);memset(y, 0, sizeof y);memset(que, 0, sizeof que);memset(stp, -1, sizeof stp);head_ = tail = 0;scanf("%d", &n);lasty = -2147483637;idx = 0;for (int i = 0; i < n; ++i) {scanf("%d%d", &tx1, &ty1);if (tx1 != lasty + 1) {x[idx] = lasty + 1;y[idx] = tx1 - 1;++idx;}lasty = ty1;}x[idx] = lasty + 1;y[idx] = 2147483637;T = idx << 1 | 1;++idx;scanf("%d", &lj);if (lj & 1 ^ 1) {puts("-1");continue;}g.clear();for (int i = 0; i < (idx << 1); i += 2) {tx1 = x[i >> 1] + (x[i >> 1] & 1? 1: 0);ty1 = y[i >> 1] - (y[i >> 1] & 1? 1: 0);for (int j = 1; j < (idx << 1); j += 2) {tx2 = x[j >> 1] + (x[j >> 1] & 1? 0: 1);ty2 = y[j >> 1] - (y[j >> 1] & 1? 0: 1);if (tx1 + lj <= ty2 && ty1 + lj >= tx2 || tx1 - lj <= ty2 && ty1 - lj >= tx2) {g.ist(i, j);}}}for (int i = 1; i < (idx << 1); i += 2) {tx1 = x[i >> 1] + (x[i >> 1] & 1? 0: 1);ty1 = y[i >> 1] - (y[i >> 1] & 1? 0: 1);for (int j = 0; j < (idx << 1); j += 2) {tx2 = x[j >> 1] + (x[j >> 1] & 1? 1: 0);ty2 = y[j >> 1] - (y[j >> 1] & 1? 1: 0);if (tx1 + lj <= ty2 && ty1 + lj >= tx2 || tx1 - lj <= ty2 && ty1 - lj >= tx2) {g.ist(i, j);}}}que[tail++] = 0;stp[0] = 0;while (head_ != tail) {h = que[head_++];for (int j = g.head[h]; j != -1; j = g.next[j]) {if (stp[g.to[j]] == -1) {stp[g.to[j]] = stp[h] + 1;que[tail++] = g.to[j];}}}printf("%d\n", stp[T]);}return 0;
}