#include <iostream>
#include <fstream>
#include <vector>
#include <deque>
#include <queue>
#define dMAX (1 << 9)
#define INF (1 << 19)

using namespace std;

typedef pair<int, int> pi;

int n, m, s, de;
int x, y, c, z;
int dist[dMAX], dij[dMAX], father[dMAX], oldD[dMAX];
int pVerif, newV, cost, newD;
int currentFlow, currentCost, maxFlow, maxFlowCost;

vector<int> graf[dMAX];
vector<int> tgraf[dMAX];
deque<int> d;

priority_queue<pi, vector<pi>, greater<pi> > H;

int C[dMAX][dMAX], F[dMAX][dMAX], Z[dMAX][dMAX];

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

bool Dijkstra() {
    int i, j;
    for (i = 1; i <= n; i++) dist[i] = INF;
    dist[s] = dij[s] = 0;
    H.push({0, s});
    while (!H.empty()) {
        int cst = H.top().first, node = H.top().second;
        H.pop();
        if (dist[node] != cst) continue;
        vector<int> :: iterator it;
        for (it = graf[node].begin(); it != graf[node].end(); it++) {
            if (C[node][*it]) {
                newD = dist[node] + Z[node][*it] + oldD[node] - oldD[*it];
                if (newD < dist[*it]) {
                    dist[*it] = newD;
                    dij[*it] = dij[node] + Z[node][*it];
                    father[*it] = node;
                    H.push({dist[*it], *it});
                }
            }
        }
    }
    for (i = 1; i <= n; i++) {
        oldD[i] = dij[i];
    }
    if (dist[de] == INF) return false;
    currentFlow = INF, currentCost = 0;
    for (i = de; i != s; i = father[i]) {
        currentFlow = min(currentFlow, C[father[i]][i]);
        currentCost += Z[father[i]][i];
    }
    maxFlow += currentFlow;
    maxFlowCost += currentFlow * dij[de];
    for (i = de; i != s; i = father[i]) {
        C[father[i]][i] -= currentFlow;
        C[i][father[i]] += currentFlow;
    }
    return true;
}

void BellmanFord() {
    int i, j;
    for (i = 1; i <= n; i++) dist[i] = INF;
    dist[s] = 0;
    d.push_back(s);
    while (!d.empty()) {
        pVerif = d.front();
        d.pop_front();
        for (i = 0; i < tgraf[pVerif].size(); i++) {
            newV = tgraf[pVerif][i];
            cost = Z[pVerif][newV];
            if (dist[newV] > dist[pVerif] + cost) {
                dist[newV] = dist[pVerif] + cost;
                d.push_back(newV);
            }
        }
    }
    /*for (i = 1; i <= n; i++) {
        for (j = 1; j <= n; j++) {
            if (C[i][j]) {
                Z[i][j] = Z[i][j] + dist[i] - dist[j];
                Z[j][i] = -Z[i][j];
            }
        }
    }*/
}

int main()
{
    int i, j;
    fin >> n >> m >> s >> de;
    for (i = 1; i <= m; i++) {
        fin >> x >> y >> c >> z;
        tgraf[x].push_back(y);
        graf[x].push_back(y);
        graf[y].push_back(x);
        C[x][y] = c;
        Z[x][y] = z;
        Z[y][x] = -z;
    }

    BellmanFord();
    while (Dijkstra()) {

    }
    fout << maxFlowCost;
    return 0;
}