#include<bits/stdc++.h>
#define ull unsigned long long
#define ui unsigned int
#define ld long double
#define ll long long
#define lll __int128
#define fi first
#define se second
#define e emplace
#define eb emplace_back
#define db double
#define ef emplace_front
#define pii pair<int,int>
#define pll pair<ll,ll>
#define vi vector<int>
#define vp vector<pii>
#define mp make_pair

//#define LOCALJUDGE
#define int ll
bool ST;
static const ll MOD=1e9+7,Phi=998244352,inv2=499122177,Root=3,iRoot=332748118;
static const ll inf=1073741823,INF=4557430888798830399;
static const double eps=1e-8,pi=3.1415926535;
char in[1<<20],*p1=in,*p2=in;
using namespace std;
//#define getchar() (p1==p2&&(p2=(p1=in)+fread(in,1,1<<20,stdin),p1==p2)?EOF:*p1++)
struct tup{int x,y,z;tup(int X=0,int Y=0,int Z=0){x=X,y=Y,z=Z;}};
namespace FastIO
{
	template<typename T> inline void write(T x,char ch=' ')
	{
		if(is_same<char,T>::value)putchar(x);
		else
		{
			if(x<0)x=-x,putchar('-');
			static char st[25];int top=0;
			do{st[top++]=x%10+'0',x/=10;}while(x);
			while(top)putchar(st[--top]);
		}
		ch!='~'?putchar(ch):0;
	}
	inline void write(const char*x,char ch=' ')
	{
		for(int i=0;x[i]!='\0';++i)putchar(x[i]);
		ch!='~'?putchar(ch):0;
	}
	inline void read(char&s){do s=getchar();while(s=='\n'||s==' ');}
	inline void read(char s[])
	{
		int len=0;char st;
		do st=getchar();while(st=='\n'||st==' ');
		s[++len]=st,st=getchar();
		while(st!='\n'&&st!=' ')s[++len]=st,st=getchar();
		s[++len]='\0';
	}
	template<typename T> inline void read(T &s)
	{
		s=0;char ch=getchar();
		while((ch>'9'||ch<'0')&&ch!='-')ch=getchar();
		bool tf=(ch=='-')&&(ch=getchar());
		while((ch>='0')&&(ch<='9'))s=(s<<1)+(s<<3)+ch-'0',ch=getchar();
		s=(tf?-s:s);
	}
	template<typename T1,typename T2> inline void read(pair<T1,T2> &s){read(s.fi),read(s.se);}
	template<typename T,typename...Args> inline void write(T x,Args...args){write(x,'~'),write(args...);}
	template<typename T,typename...Args> inline void read(T&x,Args&...args){read(x),read(args...);}
}
using namespace FastIO;
namespace MTool
{
	inline int Cadd(int a,int b){return (ll)a+b>=MOD?(ll)a+b-MOD:a+b;}
	inline int Cdel(int a,int b){return a-b<0?a-b+MOD:a-b;}
	inline int Cmul(int a,int b){return 1ll*a*b%MOD;}
	inline int sqr(int a){return 1ll*a*a%MOD;}
	inline void Madd(int&a,int b){a=((ll)a+b>=MOD?(ll)a+b-MOD:a+b);}
	inline void Mdel(int&a,int b){a=(a-b<0?a-b+MOD:a-b);}
	inline void Mmul(int&a,int b){a=1ll*a*b%MOD;}
	template<typename T> inline bool Mmax(T&a,T b){return a<b?a=b,1:0;}
	template<typename T> inline bool Mmin(T&a,T b){return a>b?a=b,1:0;}
	template<typename...Args> inline void Madd(int&a,int b,Args...args){Madd(a,b),Madd(a,args...);}
	template<typename...Args> inline void Mmul(int&a,int b,Args...args){Mmul(a,b),Mmul(a,args...);}
	template<typename...Args> inline void Mdel(int&a,int b,Args...args){Mdel(a,b),Mdel(a,args...);}
	template<typename...Args> inline int Cadd(int a,int b,Args...args){return Cadd(Cadd(a,b),args...);}
	template<typename...Args> inline int Cmul(int a,int b,Args...args){return Cmul(Cmul(a,b),args...);}
	template<typename...Args> inline int Cdel(int a,int b,Args...args){return Cdel(Cdel(a,b),args...);}
	template<typename...Args,typename T> inline bool Mmax(T&a,T b,Args...args){return Mmax(a,b)|Mmax(a,args...);}
	template<typename...Args,typename T> inline bool Mmin(T&a,T b,Args...args){return Mmin(a,b)|Mmin(a,args...);}
	inline int power(int x,int y){int s=1;for(;y;y>>=1,Mmul(x,x))if(y&1)Mmul(s,x);return s;}
}
using namespace MTool;
namespace WrongAnswer_90
{
	int n,m,q,len,cnt,tot,s[200010],head[200010],to[400010],v[400010],nex[400010];
	int ans[200010],fin[200010],b[200010],lca[200010],rt[200010],a[200010];
	int end[200010],dfn[200010],siz[200010],dep[200010],rt1[200010];
	int son[200010],top[200010],fa[200010],id[200010];
	inline void add(int x,int y,int z){to[++cnt]=y,v[cnt]=z,nex[cnt]=head[x],head[x]=cnt;}
	vi ve[200010],tr[200010],ve2[200010],tr2[200010];
	namespace LCT
	{
		#define ls(x) t[x].ls
		#define rs(x) t[x].rs
		pii c[20000010];
		int cnt,root;
		inline int calc(int x,int y){return c[x].fi*y+c[x].se;}
		struct{int ls,rs,v;}t[20000010];
		void add(int&p,int L,int R,int x)
		{
			if(!p)return t[p=++cnt]={0,0,x},void();
			int mid=L+((R-L)>>1);
			if(calc(x,mid)<calc(t[p].v,mid))swap(x,t[p].v);
			if(calc(x,L)<calc(t[p].v,L))add(ls(p),L,mid,x);
			if(calc(x,R)<calc(t[p].v,R))add(rs(p),mid+1,R,x);
		}
		int ask(int p,int L,int R,int x)
		{
			if(!p)return INF;
			int v=calc(t[p].v,x),mid=L+((R-L)>>1);
			if(x<=mid)return min(ask(ls(p),L,mid,x),v);
			return min(ask(rs(p),mid+1,R,x),v);
		}
		void merge(int&x,int y,int L=0,int R=1e9)
		{
			if(!x||!y)return x|=y,void();
			int mid=L+((R-L)>>1);
			merge(ls(x),ls(y),L,mid),merge(rs(x),rs(y),mid+1,R);
			add(x,L,R,t[y].v);
		}
		void copy(int&now,int from,int del)
		{
			if(!from)return;
			c[++len]=c[t[from].v],c[len].se+=del,t[now=++cnt].v=len;
			copy(ls(now),ls(from),del),copy(rs(now),rs(from),del);
		}
		void print(int p,int L=0,int R=1e9)
		{
			if(!p)return;
			write(L,' ',R,' ',c[t[p].v].fi,' ',c[t[p].v].se,'\n');
			int mid=L+((R-L)>>1);
			print(ls(p),L,mid),print(rs(p),mid+1,R);
		}
		#undef ls
		#undef rs
	}
	using namespace LCT;
	namespace Segment
	{
		#define ls(x) (t[x].l+t[x].r)
		#define rs(x) (ls(x)^1)
		struct{int l,r,rt;vi ve;}t[400010];
		void build(int p,int l,int r)
		{
			t[p].l=l,t[p].r=r,t[p].rt=0,t[p].ve.clear();
			if(l==r)return t[p].rt=rt1[id[l]],void();
			int mid=l+((r-l)>>1);
			build(ls(p),l,mid),build(rs(p),mid+1,r);
		}
		void modify(int p,int l,int r,int id)
		{
			if(l<=t[p].l&&r>=t[p].r)return t[p].ve.eb(id),void();
			if(l<=t[ls(p)].r)modify(ls(p),l,r,id);
			if(r>t[ls(p)].r)modify(rs(p),l,r,id);
		}
		void solve(int p,int L,int R)
		{
			if(L<R)
			{
				int mid=L+((R-L)>>1);
				solve(ls(p),L,mid),merge(t[p].rt,t[ls(p)].rt);
				solve(rs(p),mid+1,R),merge(t[p].rt,t[rs(p)].rt);
			}
//			cerr<<L<<" "<<R<<endl;
//			print(t[p].rt);puts("");
			for(auto x:t[p].ve)Mmin(ans[x],ask(t[p].rt,0,1e9,b[x]));
		}
	}
	using namespace Segment;
	void dfs(int x,int Fa)
	{
		dep[x]=dep[fa[x]=Fa]+1,siz[x]=1;
		for(int i=head[x];i;i=nex[i])if(to[i]!=Fa)
		{
			s[to[i]]=s[x]+v[i],dfs(to[i],x),siz[x]+=siz[to[i]];
			if(siz[to[i]]>siz[son[x]])son[x]=to[i];
		}
	}
	void dfs1(int x,int topp)
	{
		top[x]=topp,id[dfn[x]=++tot]=x;
		if(son[x])dfs1(son[x],topp),end[x]=end[son[x]];
		else end[x]=tot;
		for(int i=head[x];i;i=nex[i])
		if(to[i]!=fa[x]&&to[i]!=son[x])dfs1(to[i],to[i]);
	}
	vector<tup> rl[200010];
	inline int LCA(int x,int y,int id)
	{
		while(top[x]!=top[y])
		{
			if(dep[top[x]]>dep[top[y]])
			tr[x].eb(id),ve[x].eb(id),x=fa[top[x]];
			else tr[y].eb(id),ve[y].eb(id),y=fa[top[y]];
		}
		tr[x].eb(id),tr[y].eb(id);
		rl[top[x]].eb(tup(x,y,id));
		return dep[x]<dep[y]?x:y;
	}
	inline void modify(int x,int id){while(x)tr2[x].eb(id),ve2[x].eb(id),x=fa[top[x]];}
	void dfs2(int x)
	{
		c[++len]=mp(a[x],2*s[x]),add(rt[x],0,1e9,len);
		if(son[x])dfs2(son[x]);
		for(int i=head[x];i;i=nex[i])if(to[i]!=fa[x]&&to[i]!=son[x])
		dfs2(to[i]),merge(rt[x],rt[to[i]]),root=0;
		if(x!=son[fa[x]])
		{
			for(int i=dfn[x];i<=end[x];++i)copy(rt1[id[i]],rt[id[i]],-2*s[id[i]]);
			for(int i=dfn[x];i<=end[x];++i)
			{
				merge(root,rt1[id[i]]);
				for(auto p:ve[id[i]])Mmin(ans[p],ask(root,0,1e9,b[p]));
			}
			root=0;
			for(int i=dfn[x];i<=end[x];++i)copy(rt1[id[i]],rt[id[i]],-4*s[id[i]]);
			for(int i=dfn[x];i<=end[x];++i)
			{
				merge(root,rt1[id[i]]);
				for(auto p:ve2[id[i]])Mmin(ans[p],ask(root,0,1e9,b[p])+2*s[lca[p]]);
			}
			root=0;
			for(int i=dfn[x];i<=end[x];++i)copy(rt1[id[i]],rt[id[i]],0);
			for(int i=end[x];i>=dfn[x];--i)
			{
				merge(root,rt1[id[i]]);
				for(auto p:tr2[id[i]])Mmin(ans[p],ask(root,0,1e9,b[p])-4*s[id[i]]+2*s[lca[p]]);
			}
			for(int i=dfn[x];i<=end[x];++i)copy(rt1[id[i]],rt[id[i]],-2*s[id[i]]);
			for(int i=end[x];i>=dfn[x];--i)
			{
				if(i<end[x])merge(rt[id[i]],rt[id[i+1]]);
				for(auto p:tr[id[i]])Mmin(ans[p],ask(rt[id[i]],0,1e9,b[p])-2*s[id[i]]);
			}
			build(1,dfn[x],end[x]);
			for(auto [l,r,id]:rl[x])modify(1,min(dfn[l],dfn[r]),max(dfn[l],dfn[r]),id);
			solve(1,dfn[x],end[x]);
		}
	}
	inline void mian()
	{
		read(n,m,q);int x,y,z;
		for(int i=1;i<=n;++i)read(a[i]);
		for(int i=1;i<n;++i)read(x,y,z),add(x,y,z),add(y,x,z);
		dfs(1,0),dfs1(1,1);
		for(int i=1;i<=q;++i)
		{
			read(x,y),b[i]=abs((y-1)/n-(x-1)/n),ans[i]=INF;
			modify(lca[i]=LCA(x=(x-1)%n+1,y=(y-1)%n+1,i),i);
			fin[i]=s[x]+s[y]-2*s[lca[i]];
		}
		dfs2(1);
		for(int i=1;i<=q;++i)write(fin[i]+ans[i],'\n');
	}
}
bool ED;
signed main()
{
	#ifdef LOCALJUDGE
	freopen("1.in","r",stdin);
	freopen("1.out","w",stdout);
	#endif
	double st=clock();
	WrongAnswer_90::mian();
	double ed=clock();
	#ifndef LOCALJUDGE
 	cerr<<endl;
	#endif
 	cerr<<"Time: "<<ed-st<<" ms\n";
	#ifdef LOCALJUDGE
 	cerr<<"     ";
	#endif
 	cerr<<"Memory: "<<abs(&ST-&ED)/1024.0/1024.0<<" MB\n";
	return 0;
}