/*#include<stdio.h>
#include<vector>
#include<string.h>
#include<queue>
#define inf "fmcm.in"
#define outf "fmcm.out"
#define NMax 351
#define INF 0x3f3f3f3f
using namespace std;

int N, M, S, D;
vector<int> G[NMax];
int C[NMax][NMax], Cost[NMax][NMax], F[NMax][NMax];
int go;
int Dist[NMax], From[NMax], in[NMax];

void read()
{
    scanf("%d%d%d%d", &N, &M, &S, &D);

    int x, y, c, z;
    for(int i=1; i<=M; i++) {
        scanf("%d%d%d%d", &x, &y, &c, &z);
        G[x].push_back(y);
        G[y].push_back(x);

        C[x][y] = c;
        Cost[x][y] = z;
        Cost[y][x] = -z;
    }
}

int BF() {
    for(int i=1; i<=N; i++) { Dist[i] = INF; From[i] = -1; }
    Dist[S] = 0;
	
	memset( in, 0, sizeof(in) );
    queue<int> q; 
    q.push(S); in[S] = 1;
    
    while( !q.empty() ) {
    	int u = q.front(); q.pop();
    	in[u] = 0;
    	
    	for(int i=0; i<G[u].size(); i++) {
    		int v = G[u][i];
    		if( C[u][v] - F[u][v] > 0 && Dist[u] + Cost[u][v] < Dist[v] ) {
    			Dist[v] = Dist[u] + Cost[u][v];
    			From[v] = u;
    			if( !in[v] ) { in[v] = 1; q.push(v); }
    		}
    	}
    }
    
    if( Dist[D]!=INF ) {
    	go = 1;
    	int fmin = INF, u;
    	
    	for( u=D; u!=S; u=From[u] ) fmin = min( fmin, C[From[u]][u] - F[From[u]][u] );
    	
    	for( u=D; u!=S; u=From[u] ) {
    		F[From[u]][u] += fmin;
    		F[u][From[u]] -= fmin;
    	}
    	
    	return fmin*Dist[D];
    }
    
    return 0;
}

void solve()
{
    go = 1; long long rez = 0;
    while( go ) {
        go = 0;
        rez += BF();
    }

    printf("%lld", rez);
}

int main()
{
	freopen(inf,"r",stdin); freopen(outf,"w",stdout);
	read(); solve();
	return 0;
}*/

#include <stdio.h>
#include <vector>

using namespace std;

#define maxn 510
#define inf 2000000000
#define ll long long
#define maxx 1000010

int N, M, S, D;
int Drum, L;
vector <int> A[maxn];
int G[maxn], Dist[maxn], From[maxn];
int Q[maxx], U[maxn];
int C[maxn][maxn], F[maxn][maxn], Cost[maxn][maxn];

int BellmanFord()
{
	int i, j;

	for (i = 1; i <= N; i++)
	{
		
		Dist[i] = inf;
		From[i] = -1;
	}

	Dist[S] = 0;
	L = 1;
	Q[L] = S;
	memset(U, 0, sizeof(U));
	U[S] = 1;

	for (i = 1; i <= L; i++)
	{
		for (j=0; j<G[Q[i]]; j++)
			if (C[Q[i]][A[Q[i]][j]]-F[Q[i]][A[Q[i]][j]]>0 && Dist[Q[i]]+Cost[Q[i]][A[Q[i]][j]]<Dist[A[Q[i]][j]])
			{
				Dist[A[Q[i]][j]] = Dist[Q[i]] + Cost[Q[i]][A[Q[i]][j]];
				From[A[Q[i]][j]] = Q[i];
				if (!U[A[Q[i]][j]]) 
				{
					Q[++L] = A[Q[i]][j];
					U[Q[L]] = 1;
				}
			}

		U[Q[i]] = 0;
	}

	if (Dist[D] != inf) 
	{
		int Vmin = inf;
		Drum = 1;

		for (i = D; i != S; i = From[i]) Vmin = min(Vmin, C[From[i]][i] - F[From[i]][i]);

		for (i = D; i != S; i = From[i]) 
		{
			F[From[i]][i] += Vmin;
			F[i][From[i]] -= Vmin;
		}

		return Vmin * Dist[D];
	}

	return 0;
}

ll Flux()
{
	ll Rez = 0;
	Drum = 1;

	while (Drum)
	{
		Drum = 0;
		Rez += BellmanFord();
	}

	return Rez;
}

int main()
{
	freopen("fmcm.in", "r", stdin);
	freopen("fmcm.out", "w", stdout);

	int i, x, y, z, cap;

	scanf("%d %d %d %d ", &N, &M, &S, &D);

	for (i = 1; i <= M; i++)
	{
		scanf("%d %d %d %d ", &x, &y, &cap, &z);

		A[x].push_back(y);
		A[y].push_back(x);

		C[x][y] = cap;
		Cost[x][y] = z;
		Cost[y][x] = -z;
	}

	for (i = 1; i <= N; i++) G[i] = A[i].size();

	printf("%lld\n", Flux());

	return 0;
}