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| #include <cstdio>
#include <vector>
using namespace std;
template <class Type>
void read(Type &x)
{
char c;
bool flag = false;
while ((c = getchar()) < '0' || c > '9')
c == '-' && (flag = true);
x = c - '0';
while ((c = getchar()) >= '0' && c <= '9')
x = (x << 3) + (x << 1) + c - '0';
flag && (x = ~x + 1);
}
template <class Type>
void write(Type x)
{
x < 0 && (putchar('-'), x = ~x + 1);
x > 9 && (write(x / 10), 0);
putchar(x % 10 + '0');
}
typedef long long LL;
const int N = 2e3 + 10, mod = 1e9 + 7;
int n, d, w[N], f[N];
vector <int> g[N];
void adj (int &x)
{
x += x >> 31 & mod;
}
bool cmp (int a, int b)
{
return w[a] > w[b] || (w[a] == w[b] && a < b);
}
int dfs (int x, int fa, int &st)
{
f[x] = 1;
for (int i : g[x])
if (i ^ fa && cmp(st, i) && w[st] - w[i] <= d)
f[x] = (LL)f[x] * (dfs(i, x, st) + 1) % mod;
return f[x];
}
int main ()
{
read(d), read(n);
for (int i = 1; i <= n; i++)
read(w[i]);
for (int i = 1, a, b; i < n; i++)
{
read(a), read(b);
g[a].push_back(b);
g[b].push_back(a);
}
int res = 0;
for (int i = 1; i <= n; i++)
adj(res += dfs(i, 0, i) - mod);
write(res);
return 0;
}
|