#include<bits/stdc++.h>
#define pii pair<int,int>
#define MAXN 100010

using namespace std;

const int INF = 0x3f3f3f3f;

vector<pii> grafo[2*MAXN];

deque<pii> dq;
int dist[2*MAXN];

void bfs01(int s){
dq.push_front({s, 0});
dist[s] = 0;

while(!dq.empty()){
pii v = dq.front();
dq.pop_front();
for(auto e : grafo[v.first]){
int viz = e.first;
int w = e.second;
if(dist[v.first]+w < dist[viz]){
dist[viz] = dist[v.first]+w;
if(w == 1){
dq.push_back(e);
}
else{
dq.push_front(e);
}
}
}
}
}

int main(){
int n, k1, k2, p;
scanf("%d %d %d %d", &n, &k1, &k2, &p);

for(int i = 0; i < k1; i++){
int a, b; scanf("%d %d", &a, &b);
grafo[2*a-1].push_back({2*b-1, 0});
grafo[2*b-1].push_back({2*a-1, 0});
}

for(int i = 0; i < k2; i++){
int a, b; scanf("%d %d", &a, &b);
grafo[2*a].push_back({2*b, 0});
grafo[2*b].push_back({2*a, 0});
}

int ini, fim; scanf("%d %d", &ini, &fim);

for(int i = 1; i <= 2*n; i+=2){
if(grafo[i].size() != 0 && grafo[i+1].size() != 0){
grafo[i].push_back({i+1, 1});
grafo[i+1].push_back({i, 1});
}
}

int resp1=INF, resp2=INF, resp;
if(grafo[ini*2-1].size() != 0){
memset(dist, INF, sizeof dist);
bfs01(ini*2-1);
resp1 = min(dist[fim*2-1], dist[fim*2]);
}
if(grafo[ini*2].size() != 0){
memset(dist, INF, sizeof dist);
bfs01(ini*2);
resp2 = min(dist[fim*2-1], dist[fim*2]);
}

resp = min(resp1, resp2);

if(resp == INF){
printf("-1");
return 0;
}

printf("%d", (resp+1)*p);
}