#include<iostream>
#include<fstream>
#include<queue>
#include<vector>
#include<unordered_map>
using namespace std;

int n, m, c, z, x, y, s, d;
priority_queue <pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>> > pq;
vector<vector<int>>lista;
int tati[351];
unordered_map<int, bool>label;
int flux[351][351];
int cost[351][351];
int distanta_B[351];
int distanta[351];
int distanta_r[351];

ifstream f("fmcm.in");
ofstream g("fmcm.out");

void Bellman_Ford() {
	for (int i= 1; i <= n; i++)
		distanta_B[i] = 10000000;

	queue<int> q;
	q.push(s);
	distanta_B[s] = 0;
	while (!q.empty()) {
		int x = q.front();
		q.pop();
		label[x] = 0;
		for (auto el : lista[x])
			if(flux[x][el]>0)
				if (cost[x][el] + distanta_B[x] < distanta_B[el])
				{
					distanta_B[el] = cost[x][el] + distanta_B[x];
					if (label[el] == 0) {
						label[el] = 1;
						q.push(el);
					}
				}
			
	}

}

bool Dijkstra() {
	for (int i = 1; i <= n; i++)
	{
		distanta[i] = 1000000000;
	}
	distanta[s] = 0;
	distanta_r[s] = 0;
	pq.push({ 0,s });
	while (!pq.empty()) {
		int c = pq.top().first;
		int x = pq.top().second;
		label[x] = 1;
		pq.pop();
		if (distanta[x] == c) {
			for (auto el : lista[x]) {
				if (flux[x][el] > 0 && distanta[el] > distanta[x] + distanta_B[x] + cost[x][el] - distanta_B[el])
				{
					distanta[el] = distanta[x] + distanta_B[x] + cost[x][el] - distanta_B[el];
					distanta_r[el] = distanta_r[x] + cost[x][el];
					pq.push({ distanta[el],el });
					tati[el] = x;
				}
			}
		}
	}
	return distanta[d] != 1000000000;
	
}

int main() {
	f >> n >> m >> s >> d;
	int rez = 0;
	lista.resize(n + 1);
	for(int i=1;i<=m;i++)
	{
		f>> x >> y >> c >> z;
		lista[x].push_back(y);
		lista[y].push_back(x);
		flux[x][y] = c;
		cost[x][y] = z;
		cost[y][x] = -z;
	}
	Bellman_Ford();
	while (Dijkstra()) {
		for (int i = 1; i <= n; i++)
			distanta_B[i] = distanta_r[i];
		int min1 = 100000000;
		int x = d;
		while (x != s) {
			min1 = min(min1, flux[tati[x]][x]);
			x = tati[x];
		}
		x = d;
		while (x != s) {
			flux[tati[x]][x] -= min1;
			flux[x][tati[x]] += min1;
			x = tati[x];
		}
		rez += min1 * distanta_r[d];
	}
	g<<rez;
}