#include <fstream>
#include <queue>
#include <vector>

using namespace std;

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

#define pii pair <int, int>

const int max_size = 351, INF = 2e9 + 1;

int cap[max_size][max_size], cost[max_size][max_size], d[max_size], pr[max_size], t[max_size], aux[max_size], n, s, p;
vector <int> mc[max_size];
queue <int> q;
priority_queue <pii, vector <pii>, greater <pii>> pq;

void bf ()
{
    for (int i = 1; i <= n; i++)
    {
        aux[i] = INF;
    }
    aux[s] = 0;
    q.push(s);
    while (!q.empty())
    {
        int nod = q.front();
        q.pop();
        d[nod] = 0;
        for (auto f : mc[nod])
        {
            if (aux[nod] + cost[nod][f] < aux[f] && cap[nod][f] > 0)
            {
                aux[f] = aux[nod] + cost[nod][f];
                if (d[f] == 0)
                {
                    d[f] = 1;
                    q.push(f);
                }
            }
        }
    }
}

bool djk ()
{
    for (int i = 1; i <= n; i++)
    {
        d[i] = INF;
        pr[i] = INF;
    }
    d[s] = 0;
    pr[s] = 0;
    pq.push({0, s});
    while (!pq.empty())
    {
        int val = pq.top().first, nod = pq.top().second;
        pq.pop();
        if (val == d[nod])
        {
            for (auto f : mc[nod])
            {
                if (cap[nod][f] > 0 && d[nod] + cost[nod][f] + aux[nod] - aux[f] < d[f])
                {
                    d[f] = d[nod] + cost[nod][f] + aux[nod] - aux[f];
                    pr[f] = pr[nod] + cost[nod][f];
                    t[f] = nod;
                    pq.push({d[f], f});
                }
            }
        }
    }
    return (d[p] != INF);
}

int main ()
{
    int m;
    in >> n >> m >> s >> p;
    while (m--)
    {
        int x, y, fl, price;
        in >> x >> y >> fl >> price;
        mc[x].push_back(y);
        mc[y].push_back(x);
        cap[x][y] = fl;
        cost[x][y] = price;
        cost[y][x] = -price;
    }
    bf();
    int ans = 0, maxflow = 0;
    while (djk())
    {
        int nod = p, flux = INF;
        while (nod != s)
        {
            flux = min(flux, cap[t[nod]][nod]);
            nod = t[nod];
        }
        maxflow += flux;
        nod = p;
        while (nod != s)
        {
            cap[t[nod]][nod] -= flux;
            cap[nod][t[nod]] += flux;
            nod = t[nod];
        }
        ans += flux * pr[p];
        for (int i = 1; i <= n; i++)
        {
            aux[i] = d[i];
        }
    }
    out << ans;
    in.close();
    out.close();
    return 0;
}