#include <stdio.h>
#include <string.h>
#define fin "amenzi.in"
#define fout "amenzi.out"
#define TMAX 3501
#define NMAX 151
#define MMAX 1500
struct muchie
{
 int x1,x2,c;                 //x1-plecare x2-sosire c-timp
} A[MMAX];
FILE * f;
int s[TMAX][NMAX],amenda[TMAX][NMAX],N,M,K,P;
void readData()
{
 f = fopen(fin,"r");
 fscanf(f,"%d %d %d %d",&N,&M,&K,&P);
 for(int i = 0;i<M;++i)
     fscanf(f,"%d %d %d",&A[i].x1,&A[i].x2,&A[i].c);
 for(int i = 0 ,x,y,c;i<K;++i)
    {
     fscanf(f,"%d %d %d",&x,&y,&c);
     amenda[y][x] = c;
    }
}

void init()
{
 memset(s,-1,sizeof s);
}

void query()
{
 FILE * g = fopen(fout,"w");
 for(int i = 0,x,y; i < P ; ++i)
    {
    fscanf(f,"%d %d",&x,&y);
    fprintf(g,"%d\n",s[y][x]);
    }
 fclose(f);
 fclose(g);
}

void calc()
{
 int time;
 s[0][1] = 0;
 for(int t = 1; t<TMAX ; ++t)
    {
     for(int i = 1 ;i<=N;++i)
        s[t][i] = s[t-1][i];
     for(int p=0;p<M;++p)
       if( t-(time=A[p].c) >= 0 )
         {
          if(s[t-time][A[p].x1]!=-1)
            {
             if(s[t-time][A[p].x1] > s[t][A[p].x2])
               s[t][A[p].x2] = s[t-time][A[p].x1];
            }
          if(s[t-time][A[p].x2]!=-1)
            {
             if(s[t-time][A[p].x2] > s[t][A[p].x1])
               s[t][A[p].x1] = s[t-time][A[p].x2];
            }
         }
     for(int i=1;i<=N;++i)
       if(s[t][i]!=-1) s[t][i]+=amenda[t][i];
    }
}

void afis()
{
 FILE * g = fopen(fout,"w");
 for(int i=0;i<TMAX;++i)   {
    for(int j=1;j<=N;++j)
     fprintf(g,"%d    ",s[i][j]);
    fprintf(g,"\n");
    }
}

int main()
{
 init();
 readData();
 calc();
 query();
 return 0;
}