#include <stdio.h>
#include <stdlib.h>
#define N 100000
unsigned int X = 12345;
int rand_() {
return (X *= 3) >> 1;
}
int *ej[N], eo[N];
void append(int i, int j) {
int o = eo[i]++;
if (o >= 2 && (o & o - 1) == 0)
ej[i] = (int *) realloc(ej[i], o * 2 * sizeof *ej[i]);
ej[i][o] = j;
}
int aa[N], a_;
void sort(int *ii, int l, int r) {
while (l < r) {
int i = l, j = l, k = r, i_ = ii[l + rand_() % (r - l)], tmp;
while (j < k)
if (aa[ii[j]] == aa[i_])
j++;
else if (aa[ii[j]] < aa[i_]) {
tmp = ii[i], ii[i] = ii[j], ii[j] = tmp;
i++, j++;
} else {
k--;
tmp = ii[j], ii[j] = ii[k], ii[k] = tmp;
}
sort(ii, l, i);
l = k;
}
}
int cnt;
void dfs(int p, int i) {
int o;
for (o = eo[i]; o--; ) {
int j = ej[i][o];
if (j != p)
dfs(i, j);
}
sort(ej[i], 0, eo[i]);
for (o = 0; o < eo[i]; o++) {
int j = ej[i][o];
if (j != p) {
if (aa[i] + aa[j] <= a_)
aa[i] += aa[j];
else
cnt++;
}
}
}
int main() {
int n, h, i, j;
scanf("%d%d", &n, &a_);
for (i = 0; i < n; i++)
ej[i] = (int *) malloc(2 * sizeof *ej[i]);
for (i = 0; i < n; i++)
scanf("%d", &aa[i]);
for (h = 0; h < n - 1; h++) {
scanf("%d%d", &i, &j), i--, j--;
append(i, j), append(j, i);
}
dfs(-1, 0);
printf("%d\n", cnt);
return 0;
}
