#include <algorithm>
#include <cstdio>
#include <vector>
using namespace std;

typedef long long lld;

int T = 0;

struct Vertex {
	vector< int > neighs;
	lld limit;
	double cur;
	int T_out, index;
};

inline bool operator <(const Vertex &a, const Vertex &b) {
	return a.T_out > b.T_out;
}

Vertex *nodes;

void DFS(int vertex) {
	for (unsigned i = 0; i < nodes[vertex].neighs.size(); i++)
		DFS(nodes[vertex].neighs[i]);
	nodes[vertex].T_out = ++T;
}

int main() {
	freopen("input.txt", "r", stdin); //

	int N, K;
	scanf("%d%d", &N, &K);
	nodes = new Vertex [N];
	for (int i = 0; i < N; i++) {
		scanf("%lld%lf", &nodes[i].limit, &nodes[i].cur);
		nodes[i].index = i;
	}
	for (int i = 0; i < K; i++) {
		int F, T;
		scanf("%d%d", &F, &T);
		F--;
		T--;
		nodes[F].neighs.push_back(T);
	}
	int start, target;
	lld start_adding;
	scanf("%d%lld%d", &start, &start_adding, &target);
	start--;
	target--;

	DFS(start);
	sort(nodes, nodes + N);

	nodes[0].cur += start_adding;
	int i;
	for (i = 0; i < N; i++) {
		printf("%d:\n", nodes[i].index); //
		if (nodes[i].cur > nodes[i].limit) {
			double adding = (nodes[i].cur - nodes[i].limit) / nodes[i].neighs.size();
			printf("    adding = %.2lf\n", adding); //
			for (unsigned j = 0; j < nodes[i].neighs.size(); i++)
				nodes[nodes[i].neighs[j]].cur += adding;
		}
	}
	printf("%.4lf\n", min(nodes[i].cur, static_cast< double > (nodes[i].limit)));
	return 0;
}