#include <bits/stdc++.h>
#define F first
#define S second
 
using namespace std;
 
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
vector <int> gf[351], gft[351];
int cap[351][351], flux[351][351], cost[351][351];
int n, m, s, d, rezultat;
 
int dist[351];
void bellman_ford()
{
	for(int i = 1; i <= n; i++)
		if(i != s)
			dist[i] = 1 << 26;
 
	queue <int> q;
	bitset <351> inQ;
	q.push(s);
	inQ[s] = 1;
 
	while(!q.empty())
	{
		int nod = q.front();
		q.pop();
		inQ[nod] = 0;
 
		for(auto vec:gf[nod])
			if(dist[nod] + cost[nod][vec] < dist[vec])
			{
				dist[vec] = dist[nod] + cost[nod][vec];
				if(!inQ[vec])
				{
					q.push(vec);
					inQ[vec] = 1;
				}
			}
	}
}
int positiveDist[351], tata[351], tabelTata[351], newDist[351];
bool djikstra()
{
	for(int i = 1; i <= n; i++)
		if(i != s)
			positiveDist[i] = 1 << 26;
 
	priority_queue <pair<int, int>> pq;
	bitset <351> viz;
	pq.push({0, s});
 
	while(!pq.empty())
	{
		int nod = pq.top().second;
		pq.pop();
 
		if(viz[nod] == 1)
			continue;
		viz[nod] = 1;
 
		for(auto vec:gf[nod])
		{
			int positiveArc = cost[nod][vec] + dist[nod] - dist[vec];
			if(cap[nod][vec] && positiveDist[nod] + positiveArc < positiveDist[vec])
			{
				positiveDist[vec] = positiveDist[nod] + positiveArc;
				pq.push({-positiveDist[vec], vec});
				newDist[vec] = newDist[nod] + cost[nod][vec];
 
				tata[vec] = nod;
				tabelTata[vec] = 1;
			}
		}
 
		for(auto vec:gft[nod])
		{
			int positiveArc = -cost[vec][nod] + dist[nod] - dist[vec];
			if(flux[nod][vec] && positiveDist[nod] + positiveArc < positiveDist[vec])
			{
				positiveDist[vec] = positiveDist[nod] + positiveArc;
				pq.push({-positiveDist[vec], vec});
				newDist[vec] = newDist[nod] - cost[vec][nod];
 
				tata[vec] = nod;
				tabelTata[vec] = 2;
			}
		}
	}
 
	for(int i = 1; i <= n; i++)
		dist[i] = newDist[i];
 
	if(positiveDist[d] != (1 << 26))
		return true;
	return false;
}
pair <int, int> muchie[351];
int tabel[351];
void drum(int lung)
{
	int minim = 1 << 26, suma = 0;
 
	for(int i = 1; i <= lung; i++)
		if(tabel[i] == 1)
			minim = min(minim, cap[ muchie[i].F ][ muchie[i].S ]);
		else
			minim = min(minim, flux[ muchie[i].F ][ muchie[i].S ]);
 
	for(int i = 1; i <= lung; i++)
		if(tabel[i] == 1)
		{
			suma += cost[ muchie[i].F ][ muchie[i].S ] * minim;
			cap[ muchie[i].F ][ muchie[i].S ] -= minim;
			flux[ muchie[i].S ][ muchie[i].F ] += minim;
		}
		else
		{
			suma += -cost[ muchie[i].S ][ muchie[i].F ] * minim;
			flux[ muchie[i].F ][ muchie[i].S ] -= minim;
			cap[ muchie[i].S ][ muchie[i].F ] += minim;
		}
 
	rezultat += suma;
}
 
int main()
{
	fin >> n >> m >> s >> d;
 
	for(int k = 1, i, j, Cap, Cost; k <= m; k++)
	{
		fin >> i >> j >> Cap >> Cost;
 
		gf[i].push_back(j);
		gft[j].push_back(i);
		cap[i][j] = Cap;
		cost[i][j] = Cost;
	}
 
	bellman_ford();
 
	while(djikstra())
	{
		int nod = d, vf = 0;
		while(nod != s)
		{
			muchie[++vf] = {tata[nod], nod};
			tabel[vf] = tabelTata[nod];
			nod = tata[nod];
		}
		
		drum(vf);
	}
 
	fout << rezultat;
	return 0;
}