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#include <cstdio>
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#include <cstring>
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#include <algorithm>
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using namespace std;
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struct Tree
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{
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    int ch[2];
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    int v;
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} Node[100005];
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int a[100005], Ind, val[100005], c[100005];
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void dfs(int rt)
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{
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    if (rt)
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    {
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        dfs(Node[rt].ch[0]);
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        a[++Ind] = Node[rt].v;
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        dfs(Node[rt].ch[1]);
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    }
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}
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int f[100005], Max[100005];
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int tot;
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inline int lowbit(int x) { return x & (-x); }
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void Update(int x, int val)
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{
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    for (int i = x; i <= tot; i += lowbit(i))
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        Max[i] = max(Max[i], val);
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    return;
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}
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int Query(int x)
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{
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    int ans = 0;
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    for (int i = x; i; i -= lowbit(i))
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        ans = max(ans, Max[i]);
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    return ans;
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}
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int main()
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{
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    int n;
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    scanf("%d", &n);
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    for (int i = 1; i <= n; i++)
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    {
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        scanf("%d", &Node[i].v);
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    }
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    int fa, d;
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    for (int i = 2; i <= n; i++)
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    {
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        scanf("%d%d", &fa, &d);
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        Node[fa].ch[d] = i;
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    }
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    dfs(1);
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    //memset(f, 0x7f, sizeof(f));
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    for (int i = 1; i <= n; i++)
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    {
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        a[i] = a[i] - i;
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        c[i] = a[i];
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    }
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    int ans = 0;
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    sort(a + 1, a + n + 1);
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    tot = unique(a + 1, a + n + 1) - a - 1;
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    for (int i = 1; i <= n; i++)
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    {
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        int now = lower_bound(a + 1, a + tot + 1, c[i]) - a;
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        f[i] = Query(now) + 1;
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        Update(now, f[i]);
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        ans = max(ans, f[i]);
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    }
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    printf("%d", n - ans);
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    //while(1);
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}