#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <vector>

using namespace std;

inline int next_int() {
	int d;
	scanf("%d", &d);
	return d;
}

const int INF = 1e9;
const int V = 351;
const int E = 12501;

int n, m, s, d;
int where, cost, flow, min_cost, max_flow, dist[V], prev[V];

vector<pair<int, int> > edges;
int capacity_e[V][V], cost_e[V][V];

void mcmf() {
	while (true) {
		for (int i = 1; i <= n; i++) {
			dist[i] = INF;
			prev[i] = -1;
		}
		dist[s] = 0;
		for (int i = 1; i < n; i++) {
			for (int j = edges.size() - 1; j >= 0; j--) {
				int u = edges[j].first, v = edges[j].second;
				if (dist[u] < INF && capacity_e[u][v] > 0 && dist[u] + cost_e[u][v] < dist[v]) {
					dist[v] = dist[u] + cost_e[u][v];
					prev[v] = u;
				}
			}
		}
		if (dist[d] == INF) {
			return;
		}
		flow = INF, cost = 0, where = d;
		while (prev[where] != -1) {
			flow = min(flow, capacity_e[prev[where]][where]);
			where = prev[where];
		}
		where = d;
		while (prev[where] != -1) {
			capacity_e[prev[where]][where] -= flow;
			capacity_e[where][prev[where]] += flow;
			cost += cost_e[prev[where]][where];
			where = prev[where];
		}
		min_cost += flow * cost;
		max_flow += flow;
	}
}
int main() {
	freopen("fmcm.in", "r", stdin);
	freopen("fmcm.out", "w", stdout);
	n = next_int();
	m = next_int();
	s = next_int();
	d = next_int();
	for (int i = 0; i < m; i++) {
		int x = next_int();
		int y = next_int();
		int c = next_int();
		int z = next_int();
		capacity_e[x][y] = c, cost_e[x][y] = +z;
		capacity_e[y][x] = 0, cost_e[y][x] = -z;
		edges.push_back(make_pair(x, y));
		edges.push_back(make_pair(y, x));
	}
	mcmf();
	printf("%d\n", min_cost);
	return 0;
}