#include <fstream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstring>

using namespace std;

ifstream cin("fmcm.in");
ofstream cout("fmcm.out");

constexpr int INF = 1e9;

int n, m, source, sink;
vector<pair<int,int>> L[355];
int cap[355][355], flux[355][355], cost[355][355];
int tata[355];

bool bf()
{
	memset(tata, 0, sizeof(tata));
	vector<int> d(n+1, INF);
	d[source] = 0;
	queue<int> Q;
	Q.push(source);
	while (!Q.empty())
	{
		auto aux = Q.front(); Q.pop();
		for (auto i : L[aux])
			if (flux[aux][i.first] < cap[aux][i.first] && d[i.first] > i.second + d[aux])
			{
				d[i.first] = i.second + d[aux];
				tata[i.first] = aux;
				Q.push(i.first);
			}
	}
	return d[sink] != INF;
}

int main()
{
    cin >> n >> m >> source >> sink;
	for (int i=1;i<=m;i++)
	{
		int x, y, z, c;
		cin >> x >> y >> z >> c;
		cap[x][y] += z;
		cost[x][y] += c;
		cost[y][x] -= c;
		L[x].emplace_back(y,c);
		L[y].emplace_back(x,-c);
	}
	int ans = 0;
	while (bf())
	{
		int nod = sink;
		int minim = INF;
		while (nod != source)
		{
			minim = min(minim, cap[tata[nod]][nod] - flux[tata[nod]][nod]);
			nod = tata[nod];
		}
		nod = sink;
		while (nod != source)
		{
			flux[tata[nod]][nod] += minim;
			flux[nod][tata[nod]] -= minim;
			ans += minim * cost[tata[nod]][nod];
			nod = tata[nod];
		}
	}
	cout << ans << '\n';
    return 0;
}