#include <bits/stdc++.h>
#define rep(i,j,k) for(int i=(j);i<=(k);i++)
#define per(i,j,k) for(int i=(j);i>=(k);i--)
#define uint unsigned int
#define ll long long
#define ull unsigned long long
#define db double
#define ldb long double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define mkp make_pair
#define eb emplace_back
#define SZ(S) (int)S.size()
//#define mod 998244353
//#define mod 1000000007
#define inf 0x3f3f3f3f
#define linf 0x3f3f3f3f3f3f3f3f
using namespace std;

template <class T>
void chkmax(T &x,T y){
	if(x < y) x = y;
}

template <class T>
void chkmin(T &x,T y){
	if(x > y) x = y;
}

inline int popcnt(int x){
	return __builtin_popcount(x);
}

inline int ctz(int x){
	return __builtin_ctz(x);
}


/*ll power(ll p,int k = mod - 2){
	ll ans = 1;
	while(k){
		if(k % 2 == 1) ans = ans * p % mod;
		p = p * p % mod;
		k /= 2;	
	}
	return ans;
}*/
int n,m1,m2,_m1,_m2;
ll m;

struct eg{
	int u,v,w;
}E[2][200005],Q[2][200005];

bool cmp(eg p,eg q){
	return p.w < q.w;
}

ll result;
int fa[200005],col[200005],occ[200005],buc[2][200005];
vector <int> S[200005];
vector <pii> P[200005];
int fnd(int u){
	if(fa[u] == u) return u;
	return fa[u] = fnd(fa[u]);
}

void mrg(int u,int v){
//	printf("mrg %d %d\n",u,v);
	for(int p:S[u]) buc[0][col[p]]++;
	for(int p:S[v]) buc[1][col[p]]++;
/*	printf("Set %d:",u);
	for(int p:S[u]) printf("(%d,%d) ",p,col[p]);
	printf("\n");
	printf("Set %d:",v);
	for(int p:S[v]) printf("(%d,%d) ",p,col[p]);
	printf("\n");*/
	result += 1ll * SZ(S[u]) * SZ(S[v]);
	rep(c,1,n){
		result -= 1ll * buc[0][c] * buc[1][c];
//		printf("col %d [0]%d [1]%d\n",c,buc[0][c],buc[1][c]);
		buc[0][c] = buc[1][c] = 0; 
	}
	if(SZ(S[u]) < SZ(S[v])) swap(S[u],S[v]);
	for(int p:S[v]){
		S[u].eb(p);
		fa[p] = u;
	}
}

void smrg(vector <pii> &info,int u,int v){
	u = fnd(u);v = fnd(v);
	if(SZ(S[u]) < SZ(S[v])) swap(u,v);
	for(int p:S[v]){
		S[u].eb(p);
		fa[p] = u;
		info.eb(p,v);
	}
}

void fix(int &u){
	u = fa[u];
}

void chg(int u,int c){
//	assert(0);
	int fu = fa[u];
	result--;
	for(int p:S[fu]){
		if(col[p] == col[u]) result++;
		else if(col[p] == c) result--;
	}
	col[u] = c;

	result += occ[col[u]] - 1;
	result -= occ[c];
	occ[col[u]]--;
	occ[c]++;
}

int main(){
//	freopen("test.in","r",stdin);
//	freopen("test.out","w",stdout);
	scanf("%d%d%d%lld",&n,&m1,&m2,&m);
	rep(i,1,m1) scanf("%d%d%d",&E[0][i].u,&E[0][i].v,&E[0][i].w);
	rep(i,1,m2) scanf("%d%d%d",&E[1][i].u,&E[1][i].v,&E[1][i].w);
	sort(E[0] + 1,E[0] + m1 + 1,cmp);
	sort(E[1] + 1,E[1] + m2 + 1,cmp);
	rep(u,1,n){
		fa[u] = u;
		S[u].eb(u);
	}
	rep(i,1,m1){
		fix(E[0][i].u);fix(E[0][i].v);
		if(E[0][i].u != E[0][i].v){
			Q[0][++_m1] = E[0][i];
			smrg(P[i],E[0][i].u,E[0][i].v);
		}
	}
	rep(u,1,n){
		col[u] = fa[u];
		result += occ[col[u]];
		occ[col[u]]++;
		fa[u] = u;
		S[u].clear();
		S[u].eb(u);
	}	
//	rep(u,1,n) printf("%d ",col[u]);
//	printf("\nresult=%lld\n",result);

	m1 = _m1;
	rep(i,1,m1) E[0][i] = Q[0][i];
	int j = m1,answer = inf + inf;
	rep(i,1,m2){
		fix(E[1][i].u);fix(E[1][i].v);
		if(E[1][i].u == E[1][i].v) continue;
		mrg(E[1][i].u,E[1][i].v);
//		printf("i=%d result %lld\n",i,result);
		while(result >= m && j >= 0){
			chkmin(answer,E[1][i].w + E[0][j].w);
			for(pii I:P[j]) chg(I.first,I.second);
			j--;
		}
	}
	if(answer == inf + inf) printf("-1\n");
	else printf("%d\n",answer);
	return 0;
}