#include <bits/stdc++.h>

class InParser {
private:
	FILE *fin;
	char *buff;
	int sp;

	char read_ch() {
		++sp;
		if (sp == 4096) {
			sp = 0;
			fread(buff, 1, 4096, fin);
		}
		return buff[sp];
	}

public:
	InParser(const char* nume) {
		fin = fopen(nume, "r");
		buff = new char[4096]();
		sp = 4095;
	}

	InParser& operator >> (int &n) {
		char c;
		while (!isdigit(c = read_ch()) && c != '-');
		int sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}

	InParser& operator >> (long long &n) {
		char c;
		n = 0;
		while (!isdigit(c = read_ch()) && c != '-');
		long long sgn = 1;
		if (c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while (isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}
};

int max(int x, int y) {
    if (x > y) return x;
    return y;
}

#define int_pair std::pair <int, int>
#define MAXN  155
#define MAXT 3505

int N, M, K, P;
int DP[2*MAXT][MAXN], Pay[2*MAXT][MAXN];
std::vector <int_pair> ADC[MAXN];

inline void AddEdge(int X, int Y, int W) {
    ADC[X].push_back({Y, W});
    ADC[Y].push_back({X, W});
}

void Dynamic() {
    for (int j=0, i; j<MAXN; ++j)
        for (i=0; i<MAXT; ++i)
            DP[i][j] = -1;

    DP[0][1] = Pay[0][1];
    for (int i=0, j; i+1<MAXT; ++i)
        for (j=1; j<=N; ++j) if (DP[i][j] > -1) {
            DP[i+1][j] = std::max(DP[i+1][j], DP[i][j] + Pay[i+1][j]);
            for (int_pair Edge:ADC[j])
                DP[i + Edge.second][Edge.first] = std::max(DP[i][j] + Pay[i + Edge.second][Edge.first], DP[i + Edge.second][Edge.first]);
        }
}

InParser      In ("amenzi.in");
std::ofstream Out("amenzi.out");

void Citire() {
    In >> N >> M >> K >> P;
    for (int i=0, x, y, w; i<M; ++i)
        In >> x >> y >> w, AddEdge(x, y, w);
    for (int i=0, a, t, s; i<K; ++i)
        In >> a >> t >> s, Pay[t][a] += s;
}

void Rezolvare() {
    Dynamic();
    for (int i=0, x, y; i<P; ++i)
        In >> x >> y, Out << DP[y][x] << '\n';
}

int main()
{
    Citire();
    Rezolvare();

    return 0;
}