#include<bits/stdc++.h>
#define I long long
using namespace std;const I N=2e6;I n,q,w[N],d[N],M[N],S[N],a[N],b[N],p[N],c,h[N],f[N],t[N],s[N],m;struct o{I v,w,X;}e[N];void j(I x){S[x]=1;for(I i=h[x];i;i=e[i].X)if(e[i].v!=f[x]){I v=e[i].v;p[v]=p[x]+e[i].w;f[v]=x;d[v]=d[x]+1;j(v);S[x]+=S[v];if(S[v]>S[s[x]])s[x]=v;}}void z(I x,I T){t[x]=T;for(I i=h[x],v;i;i=e[i].X)if(e[i].v!=f[x]){v=e[i].v,z(v,v==s[x]?T:v);}}I L(I u,I v){while(t[u]!=t[v]){if(d[t[u]]<d[t[v]])swap(u,v);u=f[t[u]];}return d[u]<d[v]?u:v;}
#define _(u,v)(p[u]+p[v]-2*p[L(u,v)])
main(){cin>>n>>q;for(I i=1;i<=n;i++)cin>>w[i],M[min(n,w[i])]=i;for(I i=1,u,v,w;i<n;i++){cin>>u>>v>>w;e[++c]=(o){v,w,h[u]};h[u]=c;e[++c]=(o){u,w,h[v]};h[v]=c;}j(1);z(1,1);while(M[m])++m;a[0]=b[0]=M[0];for(I i=1;i<m;i++){I x=a[i-1],y=b[i-1],w=_(x,y),t=M[i],r=_(x,t)>_(y,t)?x:y;if(_(r,t)>w)a[i]=r,b[i]=t;else a[i]=x,b[i]=y;}while(q--){I x,d,l=0,r=m-1,k=m;cin>>x>>d;while(l<=r){I i=(l+r)>>1;if(_(a[i],x)>d||_(b[i],x)>d)k=i,r=i-1;else l=i+1;}cout<<k<<'\n';}}