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

using namespace std;

const int NMAX = 355;
const int inf = 1e9 + 5;

int n, m, s, t;
vector <int> graph[NMAX];

int cap[NMAX][NMAX];
int cost[NMAX][NMAX];

int father[NMAX];
int dist[NMAX];

queue <int> coada;
bool in_queue[NMAX];

inline bool bellman () {
    for (int i = 1; i <= n; ++ i) {
        in_queue[i] = false;
        father[i] = 0;
        dist[i] = inf;
    }

    coada.push(s);
    in_queue[s] = true;
    dist[s] = 0;

    int y;
    while (!coada.empty()) {
        y = coada.front();
        coada.pop();

        for (auto it: graph[y])
            if (cap[y][it] && dist[y] + cost[y][it] < dist[it]) {
                dist[it] = dist[y] + cost[y][it];
                father[it] = y;

                if (!in_queue[it]) {
                    in_queue[it] = true;
                    coada.push(it);
                }
            }
    }

    return dist[t] < inf;
}

inline int mincost_flow () {
    int flow = 0;
    int suma = 0;

    while (bellman()) {
        int node = t;
        int minim = inf;

        while (father[node]) {
            if (cap[father[node]][node] < minim)
                minim = cap[father[node]][node];
            node = father[node];
        }

        flow += minim;
        node = t;

        while (father[node]) {
            cap[father[node]][node] -= minim;
            cap[node][father[node]] += minim;

            suma += minim * cost[father[node]][node];

            node = father[node];
        }
    }

    return suma;
}

int main()
{
    ifstream cin("fmcm.in");
    ofstream cout("fmcm.out");

    cin >> n >> m >> s >> t;

    int x, y, c, d;
    while (m --) {
        cin >> x >> y >> c >> d;

        cap[x][y] = c;

        cost[x][y] = d;
        cost[y][x] = -d;

        graph[x].push_back(y);
        graph[y].push_back(x);
    }

    cout << mincost_flow() << '\n';

    cin.close();
    cout.close();
    return 0;
}