#include<stdio.h>
#define mt 3500
#define INF -42000000
typedef struct nod {int x,c; nod *d; } nod;
typedef struct amenda { int x,c; amenda *d; } amenda;

nod *v[160];
amenda *a[3600];
int n,m,k,p;
long s[3600][160];

void addn(int x,int y,int c)
{
  nod *p=new nod;
  p->x=x;
  p->c=c;
  p->d=v[y];
  v[y]=p;
}

void adda(int x,int y,int c)
{
  amenda *p=new amenda;
  p->x=x;
  p->c=c;
  p->d=a[y];
  a[y]=p;
}

void SOLVE();

void READ()
{ int i,x,y,c;
  FILE *f,*g;
  f=fopen("amenzi.in","r");
  g=fopen("amenzi.out","w");
  fscanf(f,"%d %d %d %d",&n,&m,&k,&p);

  for(i=1;i<=m;i++)
  { fscanf(f,"%d %d %d",&x,&y,&c);
	 addn(x,y,c);
	 addn(y,x,c); }

  for(i=1;i<=k;i++)
  {	fscanf(f,"%d %d %d",&x,&y,&c);
		adda(x,y,c);
  }

  SOLVE();
  for(i=1;i<=p;i++)
  { fscanf(f,"%d %d",&x,&y);
	if(s[y][x]!=INF) fprintf(g,"%ld\n",s[y][x]);
	else fprintf(g,"-1\n");
  }
  fclose(f);
  fclose(g);
}

void SOLVE()
{ int i,j,x,t,c;
  nod *q;
  amenda *p;
  for(i=0;i<=mt;i++)
	 for(j=1;j<=n;j++)
		s[i][j]=INF;
  s[0][1]=0;

  p=a[0];
  while(p)
  {if(p->x==1) s[0][1]+=p->c;  p=p->d; }

  for(i=1;i<=mt;i++)
  {
	  for(j=1;j<=n;j++)
	  { q=v[j];
		 s[i][j]=s[i-1][j];
		 while(q)
		 {
			x=q->x;
			t=q->c;
			if(i-t>=0 && s[i][j]<s[i-t][x]) s[i][j]=s[i-t][x];
			q=q->d;
		 }
	  }


	  p=a[i];
	  while(p)
	  {
		 j=p->x;
		 c=p->c;
		 if(s[i][j]!=INF) s[i][j]+=c;
		 p=p->d;
	  }

  }

}



int main()
{
READ();
return 0;
}