#include<cstdio>
#include<iostream>
#include<set>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;

const int INF = 1<<30;
const int NMAX = 355;
const int MMAX = 12505;

int N, M, S, D;
int REZ;
int FLUX;
int tata[NMAX];
vector<int> G[NMAX];
int C[NMAX][NMAX];
int F[NMAX][NMAX];
int s[NMAX][NMAX];
int DRUM;
int d[NMAX];

struct cmp
{
	bool operator()(const int &a, const int &b) const
	{
		return d[a] > d[b];
	}
};

/*void write()
{
	for(int i = 1 ; i <= N ; i++)
	{
		for(int j = 1 ; j <= N ; j++)
			printf("%d ", s[i][j]);
		printf("\n");
	}
	printf("\n\n\n");
}*/

void citi()
{
	int x, y, cap, cost;
	cin >> N >> M >> S >> D;
	for(int i = 1 ; i <= M ; i++)
	{
		cin >> x >> y >> cap >> cost;
		G[x].push_back(y);
		G[y].push_back(x);
		C[x][y] = cap;
		s[x][y] = cost;
		s[y][x] = -cost;
	}
}

bool dijkstra()
{
	priority_queue<int, vector<int>, cmp > Q;
	bool in_heap[NMAX] = {0};
	//bool succes = 0;
	
	fill(d + 1, d + N + 1, INF);
	/*//*/fill(tata + 1, tata + N + 1, -1);
	d[S] = 0;
	in_heap[S] = 1;
	
	Q.push(S);
	while(!Q.empty())
	{
		int nod = Q.top();
		Q.pop();
		in_heap[nod] = 0;
		for(vector<int> :: iterator it = G[nod].begin() ; it != G[nod].end() ; it++)
			if(d[nod] + s[nod][*it] < d[*it] && F[nod][*it] < C[nod][*it])
			{
				d[*it] = d[nod] + s[nod][*it];
				tata[*it] = nod;
				if(!in_heap[*it])
				{					
					Q.push(*it);
					in_heap[*it] = 1;
				}
			}
	}
	
	return d[D] < INF;
}

int main()
{
	freopen("fmcm.in", "r", stdin);
	freopen("fmcm.out", "w", stdout);
	citi();
	while(1)
	{
		if(!dijkstra())
			break;
		FLUX = INF;
		for(int nod = D ; nod != S ; nod = tata[nod])
			FLUX = min(FLUX, C[tata[nod]][nod] - F[tata[nod]][nod]);
		REZ += d[D] * FLUX;
		for(int nod = D ; nod != S ; nod = tata[nod])
		{
			F[tata[nod]][nod] += FLUX;
			F[nod][tata[nod]] -= FLUX;
		}
	}
	
	printf("%d\n", REZ);
	
	return 0;
}