#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <vector>
#include <algorithm>
using namespace std;

const int NMAX = 360, INF = 0x3f3f3f3f;

int N, M, Source, Sink, X, Y, Z, C, Cap[NMAX][NMAX], Flow[NMAX][NMAX], Cost[NMAX][NMAX], Father[NMAX], Dist[NMAX];
vector<int> G[NMAX];
bool InQueue[NMAX];

bool BellmanFord()
{
    for(int i = 1; i <= N; ++ i) Dist[i] = INF, Father[i] = InQueue[i] = 0;
    Dist[Source] = 0;
    queue<int> Q;
    Q.push(Source);

    while(!Q.empty())
    {
        int Node = Q.front();
        Q.pop();
        InQueue[Node] = 0;

        for(vector<int> :: iterator it = G[Node].begin(); it != G[Node].end(); ++ it)
            if(Cap[Node][*it] > Flow[Node][*it] && Dist[*it] > Dist[Node] + Cost[Node][*it])
            {
                Dist[*it] = Dist[Node] + Cost[Node][*it];
                Father[*it] = Node;
                if(!InQueue[*it])
                    InQueue[*it] = 1, Q.push(*it);
            }
    }
    return Dist[Sink] != INF;
}

void FMCM()
{
    int Ans = 0;
    while(BellmanFord())
    {
        int MinFlow = INF;
        for(int Node = Sink; Node != Source; Node = Father[Node])
            MinFlow = min(MinFlow, Cap[Father[Node]][Node] - Flow[Father[Node]][Node]);
        for(int Node = Sink; Node != Source; Node = Father[Node])
        {
            Flow[Father[Node]][Node] += MinFlow;
            Flow[Node][Father[Node]] -= MinFlow;
        }
        Ans += MinFlow * Dist[Sink];
    }

    printf("%i\n", Ans);
}

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

    scanf("%i %i %i %i", &N, &M, &Source, &Sink);
    for(int i = 1; i <= M; ++ i)
    {
        scanf("%i %i %i %i", &X, &Y, &Z, &C);
        G[X].push_back(Y);
        G[Y].push_back(X);
        Cap[X][Y] = Z;
        Cost[X][Y] = C;
        Cost[Y][X] = -C;
    }

    FMCM();
}