#include <iostream>
#include <string>
#include <vector>


using namespace std;
static const int N = 10;
int main(int argc, char **argv)


{
    int i,p,q,id[N];
    for(i = 0;i < N;i++)id[i] = i;

    int kk = 0; //mosti
    int jj = 0; //ostrova
    int n1,n2, hh;
    cin >> hh >> kk >> n1 >> n2;
    for(int i = 0; i<kk;i++){
        cin >> p >> q;
        for(int g = 0 ; g < N;g++){
            if(id[g] == id[p]) id[g] = id[q];
        }
    }

    cin >> jj;
    for(int i = 0; i < jj;i++){
        int h;
        cin >>h;
        for(int j = 0;j < N;j++)
            if(j ==h)id[j] = -1000;


    }

    if(id[n1] == id[n2] && id[n1] >=0)
        cout << "yes" << endl;
    else{
        cout << "no" << endl;
    }


    return 0;
}