#include <bits/stdc++.h>
using namespace std;
const int N=2e5+10;
typedef long long ll;

int n,m,q;
int a[N];
pair<int,int> b[N];
vector<pair<int,ll> > g[N];
int f[N],dep[N],siz[N],son[N],dfn[N],num,rnk[N],top[N];
ll dis[N];
pair<pair<int,int>,pair<int,int> > ask[N];
ll ans[N];

void dfs1(int u,int fa) {
	f[u]=fa;
	dep[u]=dep[fa]+1;
	siz[u]=1;
	for(auto i:g[u]) {
		int v=i.first;
		ll w=i.second;
		if(v==fa) continue;
		dis[v]=dis[u]+w;
		dfs1(v,u);
		if(siz[v]>siz[son[u]]) son[u]=v;
		siz[u]+=siz[v];
	}
}

void dfs2(int u,int tp) {
	dfn[u]=++num,rnk[num]=u;
	top[u]=tp;
	if(son[u]) dfs2(son[u],tp);
	for(auto i:g[u]) {
		int v=i.first;
		ll w=i.second;
		if(v==f[u] || v==son[u]) continue;
		dfs2(v,v);
	}
}

int LCA(int u,int v) {
	while(top[u]!=top[v]) {
		if(dep[top[u]]<dep[top[v]]) swap(u,v);
		u=f[top[u]];
	}
	if(dep[u]>dep[v]) swap(u,v);
	return u;
}

int Dis(int u,int v) {
	return dis[u]+dis[v]-2*dis[LCA(u,v)];
}

struct Val{
	vector<pair<int,ll> > arr;
	int L;
	
	void clear() {
		arr.clear();
		L=0;
	}
	
	void ins(int x,ll y) {
		int sz=arr.size();
		while(sz>1 && (__int128)(arr[sz-1].second-arr[sz-2].second)*(x-arr[sz-1].first)>=(__int128)(y-arr[sz-1].second)*(arr[sz-1].first-arr[sz-1].first)) arr.pop_back(),sz--;
		arr.push_back({x,y});
	}
	
	ll query(int k) {
		int sz=arr.size();
		while(L<sz && arr[L+1].second-arr[L].second<=1ll*k*(arr[L+1].first-arr[L].first)) L++;
		if(L>=sz) return 1e18;
		return -1ll*k*arr[L].first+arr[L].second;
	}
};

struct Node{
	Val val;
	#define lid(x) (x<<1)
	#define rid(x) (x<<1|1)
	#define val(x) t[x].val
}t[N<<2];

void build(int id,int L,int R) {
	val(id).clear();
	if(L==R) return ;
	int mid=L+R>>1;
	build(lid(id),L,mid),build(rid(id),mid+1,R);
}

void ins(int id,int L,int R,int pos,int x,ll y) {
	val(id).ins(x,y);
	if(L==R) return ;
	int mid=L+R>>1;
	if(mid>=pos) ins(lid(id),L,mid,pos,x,y);
	else ins(rid(id),mid+1,R,pos,x,y);
}

ll query(int id,int L,int R,int l,int r,int k) {
	if(L>=l && R<=r) return val(id).query(k);
	int mid=L+R>>1;
	ll res=1e18;
	if(mid>=l) res=min(res,query(lid(id),L,mid,l,r,k));
	if(mid+1<=r) res=min(res,query(rid(id),mid+1,R,l,r,k));
	return res;
}

void ins1(int x,int k) {
	int u=x;
	while(u) {
		ins(1,1,n,dfn[u],k,2*dis[x]-2*dis[u]);
		u=f[top[u]];
	}
}

void ins2(int x,int k) {
	int u=x;
	while(u) {
		ins(1,1,n,dfn[u],k,2*dis[x]-4*dis[u]);
		u=f[top[u]];
	}
}

ll query1(int u,int v,int k) {
	ll res=1e18;
	while(top[u]!=top[v]) {
		if(dep[top[u]]<dep[top[v]]) swap(u,v);
		res=min(res,query(1,1,n,dfn[top[u]],dfn[u],-k));
		u=f[top[u]];
	}
	if(dep[u]>dep[v]) swap(u,v);
	res=min(res,query(1,1,n,dfn[u],dfn[v],-k));
	return res;
}

ll query2(int u,int k) {
	ll res=1e18;
	while(u) {
		res=min(res,query(1,1,n,dfn[top[u]],dfn[u],-k));
		u=f[top[u]];
	}
	return res;
}

int main() {
	scanf("%d%d%d",&n,&m,&q);
	for(int i=1;i<=n;i++) scanf("%d",&a[i]),b[i]={a[i],i};
	for(int i=1;i<n;i++) {
		int u,v;
		ll w;
		scanf("%d%d%lld",&u,&v,&w);
		g[u].push_back({v,w}),g[v].push_back({u,w});
	}
	dfs1(1,0);
	dfs2(1,1);
	for(int i=1;i<=q;i++) {
		ll u,v;
		scanf("%lld%lld",&u,&v);
		int uu=u%n,vv=v%n;
		if(!uu) uu=n;
		if(!vv) vv=n;
		ask[i]={{abs((u-uu)/n-(v-vv)/n),i},{uu,vv}};
		ans[i]=1e18;
	}
	sort(b+1,b+1+n),sort(ask+1,ask+1+q);
	build(1,1,n);
	for(int i=1;i<=n;i++) ins1(b[i].second,b[i].first);
	for(int i=1;i<=q;i++) ans[ask[i].first.second]=min(ans[ask[i].first.second],query1(ask[i].second.first,ask[i].second.second,ask[i].first.first));
	build(1,1,n);
	for(int i=1;i<=n;i++) ins2(b[i].second,b[i].first);
	for(int i=1;i<=q;i++) {
		int lca=LCA(ask[i].second.first,ask[i].second.second);
		ans[ask[i].first.second]=min(ans[ask[i].first.second],2*dis[lca]+query2(lca,ask[i].first.first));
	}
	for(int i=1;i<=q;i++) ans[ask[i].first.second]+=Dis(ask[i].second.first,ask[i].second.second);
	for(int i=1;i<=q;i++) printf("%lld\n",ans[i]);
	return 0;
}