//Shirasu Azusa 2024.5
#include <bits/stdc++.h>
#define fi first
#define se second
#define eb emplace_back
#define mp make_pair
using namespace std;
typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;
typedef __int128 i128;
template<class T,class S>
bool chmax(T &a,const S b) {return (a<b?a=b,1:0);}
template<class T,class S>
bool chmin(T &a,const S b) {return (a>b?a=b,1:0);}
int popcnt(int x) {return __builtin_popcount(x);}
int popcnt(ll x)  {return __builtin_popcountll(x);}
int topbit(int x) {return (x==0?-1:31-__builtin_clz(x));}
int topbit(ll x)  {return (x==0?-1:63-__builtin_clzll(x));}
int lowbit(int x) {return (x==0?-1:__builtin_ctz(x));}
int lowbit(ll x)  {return (x==0?-1:__builtin_ctzll(x));}

#define int long long
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
typedef pair<int,int> pii;  
typedef vector<int> vi;
typedef vector<pii> vp;
typedef tuple<int,int,int> tiii;
int read() {
  int x=0,w=1; char c=getchar(); 
  while(!isdigit(c)) {if(c=='-') w=-1; c=getchar();}
  while(isdigit(c)) {x=x*10+(c-'0'); c=getchar();} 
  return x*w;
}

const int N=5e5+5,inf=0x3f3f3f3f3f3f3f3f;
int dfn[N],tick,n,m,s[N],rr[N],f[N],g[N],cnt,x[N],k[N],id[N],a[N],ans[N],d[N];
vp e[N]; vi t[N];

bool cmp(const int &x,const int &y) {return dfn[x]<dfn[y];}
bool cmq(const int &a,const int &b) {return dfn[x[a]]<dfn[x[b]];}
int getg(int x,int y) {return dfn[x]<dfn[y]?x:y;}
int fr[22][N];
int lca(int u,int v) {
  if(u==v) return u; u=dfn[u], v=dfn[v]; if(u>v) swap(u,v);
  u++; int d=__lg(v-u+1); return getg(fr[d][u],fr[d][v-(1<<d)+1]);
}

void dfs(int u,int fa) {
  fr[0][dfn[u]=++tick]=fa;
  for(auto [v,w]:e[u]) if(v!=fa) s[v]=s[u]+w, d[v]=d[u]+1, dfs(v,u);
}
void pre() {
  rep(d,1,19) rep(i,1,n-(1<<d)+1) fr[d][i]=getg(fr[d-1][i],fr[d-1][i+(1<<d-1)]);
}
void work(vi a) {
  static int st[N]; int top=1; st[1]=1; vi use; use.eb(1);
  int sz=unique(a.begin(),a.end())-a.begin(); a.resize(sz);
  for(int x:a) if(x!=1) {
    int y=lca(x,st[top]);
    if(y==st[top]) st[++top]=x, use.eb(x);
    else {
      while(top>1&&d[st[top-1]]>d[y]) t[st[top-1]].eb(st[top]), top--;
      t[y].eb(st[top]), top--;
      if(st[top]!=y) assert(d[st[top]]<d[y]), st[++top]=y, use.eb(y);
      st[++top]=x, use.eb(x);
    }
  }
  while(top>1) t[st[top-1]].eb(st[top]), top--;
  for(int x:use) f[x]=g[x]=-inf;
  vi b=use; reverse(b.begin(),b.end());
  cnt=0; for(int x:a) if(rr[x]) g[x]=f[x]=0, cnt++;
  for(int u:b) {
    for(int v:t[u]) chmax(f[u],f[v]+s[v]-s[u]);
  }
  for(int u:use) {
    int mx=-inf, pmx=0, smx=-inf;
    for(int v:t[u]) {
      int gg=f[v]+s[v]-s[u];
      if(gg>mx) smx=mx, pmx=v, mx=gg;
      else chmax(smx,gg);
    }
    for(int v:t[u]) {
      int gg=max(g[u],(pmx==v?smx:mx))+s[v]-s[u];
      chmax(g[v],gg);
    }
  }
  for(int x:use) t[x].clear(), rr[x]=0;
}

void solve(int l,int r,vi p,vi q) {
  if(!q.size()) return;
  if(l==r) {
    for(int x:q) ans[x]=l;
    return;
  } int mid=l+r>>1; vi pl,pr,ql,qr;
  for(int x:p) {
    if(a[x]<=mid) pl.eb(x); else pr.eb(x);
  }
  if(pl.size()<mid-l+1) {
    solve(l,mid,pl,q); return;
  }
  vi ra=pl,rb,rc; for(int j:q) rb.eb(x[j]);
  rc.resize(ra.size()+rb.size());
  merge(ra.begin(),ra.end(),rb.begin(),rb.end(),rc.begin(),cmp);
  for(int x:pl) rr[x]=1; work(rc);
  for(int i:q) {
    int w=max(f[x[i]],g[x[i]]);
    if(w<=k[i]) qr.eb(i); else ql.eb(i);
  }
  solve(l,mid,pl,ql), solve(mid+1,r,pr,qr);
}

signed main() {
  n=read(), m=read();
  rep(i,1,n) a[i]=read();
  rep(i,2,n) {
    int u=read(), v=read(), w=read();
    e[u].eb(v,w), e[v].eb(u,w);
  }
  dfs(1,0); pre();
  rep(i,1,m) {
    x[i]=read(), k[i]=read(), id[i]=i;
  }
  vi ap,aq;
  rep(i,1,n) ap.eb(i);
  rep(i,1,m) aq.eb(i);
  sort(ap.begin(),ap.end(),cmp);
  sort(aq.begin(),aq.end(),cmq);
  solve(0,n,ap,aq);
  rep(i,1,m) printf("%lld\n",ans[i]);
  return 0;
}