#include <fstream>
#include <vector>
#include <queue>
#include <bitset>
#include <string.h>
#define inf 0x3f3f3f3f
#define nmax 350
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
int minv(int x, int y)
{
	return x < y ? x : y;
}
struct node
{
	int x, c;
	bool operator < (const node& other)const
	{
		return c > other.c;
	}
};
int n, m, S, D, t[nmax + 5], cap[nmax + 5][nmax + 5], cost[nmax + 5][nmax + 5], dist[nmax + 5], d[nmax + 5], real_d[nmax + 5], flowmax;
vector<int> g[nmax + 5];
queue<int> qb;
bitset<nmax + 5> viz;
priority_queue<node> qd;
void Bellman_Ford()
{
	int nod;
	qb.push(S);
	viz[S] = 1;
	memset(dist, inf, sizeof(dist));
	dist[S] = 0;
	while (!qb.empty())
	{
		nod = qb.front();
		qb.pop();
		viz[nod] = 0;
		for (int fiu : g[nod])
			if (cap[nod][fiu])
				if (dist[fiu] > dist[nod] + cost[nod][fiu])
				{
					dist[fiu] = dist[nod] + cost[nod][fiu];
					if (!viz[fiu])
					{
						qb.push(fiu);
						viz[fiu] = 1;
					}
				}
	}
}
bool dijkstra()
{
	int nod, cc;
	memset(t, 0, sizeof(t));
	memset(d, inf, sizeof(d));
	d[S] = 0;
	t[S] = S;
	real_d[S] = 0;
	qd.push({ S,0 });
	while (!qd.empty())
	{
		nod = qd.top().x;
		cc = qd.top().c;
		qd.pop();
		if (cc != d[nod])
			continue;
		for (int fiu : g[nod])
			if (cap[nod][fiu])
			{
				int new_d = d[nod] + (cost[nod][fiu] + dist[nod] - dist[fiu]);
				if (new_d < d[fiu])
				{
					d[fiu] = new_d;
					real_d[fiu] = real_d[nod] + cost[nod][fiu];
					t[fiu] = nod;
					qd.push({ fiu,d[fiu] });
				}
			}
	}
	for (int i = 1; i <= n; i++)
		dist[i] = real_d[i];
	if (d[D] == inf)
		return 0;
	int flow = inf;
	for (int i = D; i != S; i = t[i])
		flow = minv(flow, cap[t[i]][i]);
	for (int i = D; i != S; i = t[i])
	{
		cap[t[i]][i] -= flow;
		cap[i][t[i]] += flow;
	}
	flowmax += flow * dist[D];
	return 1;
}
int main()
{
	fin >> n >> m >> S >> D;
	int x, y, z, cc;
	for (int i = 1; i <= m; i++)
	{
		fin >> x >> y >> z >> cc;
		cap[x][y] = z;
		cost[x][y] = cc;
		cost[y][x] = -cc;
		g[x].push_back(y);
		g[y].push_back(x);
	}
	Bellman_Ford();
	while (dijkstra());
	fout << flowmax << "\n";
	return 0;
}