#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
using namespace std;

ifstream fin("fmcm.in");
ofstream fout("fmcm.out");

int n, m, sursa , destinatie;
vector<vector<int>> listaAdiacenta;
vector<vector<int>> capacitate;
vector<vector<int>> flux;
vector<vector<int>> cost;
vector<int> costbf;
vector<int> tata;
vector<bool>viz;
vector<int> costreal;
vector<int> costfictiv;

void citire()
{
    fin>> n >> m>>sursa>>destinatie;
    listaAdiacenta = vector<vector<int>>(n+1, vector<int>());
    capacitate = vector<vector<int>>(n+1, vector<int>(n+1, 0));
    flux = vector<vector<int>>(n + 1, vector<int>(n + 1, 0));
    cost = vector<vector<int>>(n + 1, vector<int>(n + 1, 0));
    int x, y, cap, cos;
    for (int i = 0; i < m; i++)
    {
        fin >> x >> y >> cap >> cos;
        listaAdiacenta[x].push_back(y);
        listaAdiacenta[y].push_back(x);
        cost[x][y] = cos;
        cost[y][x] = -cos;
        capacitate[x][y] = cap;
    }
}
// functia determina costul de a ajunge din sursa la fiecare nod folosind algoritmul Bellmanford
void bellmanFord()
{
    costbf = vector<int>(n + 1, INT_MAX);
    costbf[sursa] = 0;
    queue<int> coada;
    coada.push(sursa);
    while (!coada.empty())
    {
        int nod = coada.front();
        coada.pop();
        for (auto urm : listaAdiacenta[nod])
        {
            if (capacitate[nod][urm] > 0 && costbf[nod] + cost[nod][urm] < costbf[urm])
            {
                costbf[urm] = costbf[nod] + cost[nod][urm];
                coada.push(urm);
            }
        }
    }
}
bool dijkstra()
{
    tata = vector<int>(n + 1, -1);
    viz = vector<bool>(n + 1, false);
    costfictiv = vector<int>(n + 1, INT_MAX);
    costreal = vector<int>(n + 1, INT_MAX);
    priority_queue<pair<int,int>> coada;

    costreal[sursa] = 0;
    costfictiv[sursa] = 0;
    tata[sursa] = 0;
    coada.push({ -costfictiv[sursa],sursa });
    while (!coada.empty())
    {
        int nod = coada.top().second;
        coada.pop();
        if (viz[nod] == true)
        {
            continue;
        }
        viz[nod] = true;
        for (auto v : listaAdiacenta[nod])
        {
            int val = costfictiv[nod] + costbf[nod] - costbf[v] + cost[nod][v];
            if (flux[nod][v] < capacitate[nod][v] && val < costfictiv[v])
            {
                costfictiv[v] = val;
                costreal[v] = costreal[nod] + cost[nod][v];
                tata[v] = nod;
                coada.push({ -costfictiv[v],v });
            }
        }
    }
    for (int i = 1; i <= n; i++)
    {
        costbf[i]=costreal[i];
    }
    return tata[destinatie] != -1;
}
int fordFulkerson()
{
    int rezultat = 0;
    // determinam drumul de cost minim de la sursa la destinatie 
    while (dijkstra())
    {
        int fluxC = INT16_MAX, costTotal = 0;
        int nod = destinatie;
        // determinam fluxul lantului descoperit
        while (nod != sursa)
        {
            int pred = tata[nod];
            fluxC = min(fluxC, capacitate[pred][nod] - flux[pred][nod]);
            costTotal += cost[pred][nod];
            nod = pred;
        }
        nod = destinatie;
        // revizuim fluxurile 
        while (nod != sursa)
        {
            int pred = tata[nod];
            flux[pred][nod] += fluxC;
            flux[nod][pred] -= fluxC;
            nod = pred;
        }
        rezultat += costTotal * fluxC;
    }
    return rezultat;
}
int main()
{
    citire();
    bellmanFord();
    fout<<fordFulkerson();
}