#include <stdio.h>
#define MAXN 150
#define MAXM 1500
#define MAXT 3500
int vf[2 * MAXM + 1], next[2 * MAXM + 1], cost[2 * MAXM + 1], ult[MAXN + 1];
int infr[MAXT + 1][MAXN + 1];
int tab[MAXT + 1][MAXN + 1];

inline int max2(int a, int b){
  return a > b ? a : b;
}

inline void calctab(int n){
  int i, j, poz;
  tab[0][1] = 1 + infr[0][1];  //pe 1 il scad la final
  for(i = 0; i <= MAXT; i++){
    for(j = 1; j <= n; j++){
      poz = ult[j];
      while(poz > 0){
        if(i >= cost[poz]){
          if(tab[i - cost[poz]][vf[poz]] != 0){
            tab[i][j] = max2(tab[i - cost[poz]][vf[poz]] + infr[i][j], tab[i][j]);
          }
        }
        poz = next[poz];
      }
    }
  }
}

inline void add(int x, int y, int c, int *dr){
  vf[*dr] = y;
  cost[*dr] = c;
  next[*dr] = ult[x];
  ult[x] = *dr;
  (*dr)++;
}

int main(){
  FILE *in = fopen("amenzi.in", "r");
  int n, m, k, p, i, x, y, c, dr;
  fscanf(in, "%d%d%d%d", &n, &m, &k, &p);
  dr = 1;
  for(i = 1; i <= m; i++){
    fscanf(in, "%d%d%d", &x, &y, &c);
    add(x, y, c, &dr);
    add(y, x, c, &dr);
  }
  for(i = 1; i <= k; i++){
    fscanf(in, "%d%d%d", &x, &y, &c);
    infr[y][x] = c;
  }
  calctab(n);
  FILE *out = fopen("amenzi.out", "w");
  for(i = 0; i < p; i++){
    fscanf(in, "%d%d", &x, &y);
    fprintf(out, "%d\n", tab[y][x] - 1);
  }
  fclose(in);
  fclose(out);
  return 0;
}