#include <fstream>
#include <cstring>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <algorithm>
#include <iomanip>
#include <cmath>
#include <cstdlib>
#include <ctime>

using namespace std;
ifstream cin("fmcm.in");
ofstream cout("fmcm.out");
using ll = long long;
//#define int ll
using pi = pair<int,int>;
using pll = pair<ll, ll>;

#define pb push_back
#define x first
#define y second
struct vertex
{
    ll cost, u;
    bool operator <(const vertex &oth) const
    {
        return cost > oth.cost;
    }
};
struct edge
{
    ll a, b, c, w;
};
const ll MOD = 1e9+7, INF = 1e18, NMAX = 355;
ll cap[NMAX][NMAX], d[NMAX], p[NMAX], dist[NMAX], n, act[NMAX], cost[NMAX][NMAX], costw[NMAX];
vector<pi> v[NMAX], adj[NMAX];
vector<edge> E;
void bellmanford(int src)
{
    int i, u, nod, w;
    queue<int> q;
    for(i = 1; i <= n; i++)
        d[i] = INF;
    d[src] = 0;
    q.push(src);
    act[src] = 1;
    while(!q.empty())
    {
        u = q.front();
        q.pop();
        act[u] = 0;
        for(i = 0; i < adj[u].size(); i++)
        {
            nod = adj[u][i].x;
            w = adj[u][i].y;
            if(d[nod] > d[u] + w && cap[u][nod] > 0)
            {
                d[nod] = d[u] + w;
                if(!act[nod])
                {
                    act[nod] = 1;
                    q.push(nod);
                }
            }
        }
    }
}
int dijkstra(int src, int dest)
{
    int i, nod, w;
    vertex u;
    for(i = 1; i <= n; i++)
    {
        dist[i] = INF;
        p[i] = 0;
        costw[i] = INF;
    }
    priority_queue <vertex> pq;
    dist[src] = 0;
    costw[src] = 0;
    p[src] = src;
    pq.push({0, src});
    while(!pq.empty())
    {
        u = pq.top();
        pq.pop();
        if(u.cost > dist[u.u])
            continue;
        for(i = 0; i < v[u.u].size(); i++)
        {
            nod = v[u.u][i].x;
            w = v[u.u][i].y;
            if(dist[nod] > u.cost + w + d[u.u] - d[nod] && cap[u.u][nod] > 0)
            {
                dist[nod] = u.cost + w + d[u.u] - d[nod];
                costw[nod] = costw[u.u] + w;
                p[nod] = u.u;
                pq.push({dist[nod], nod});
            }
        }
    }
    return dist[dest] != INF;
}
void solve()
{
    ll m, i, j, src, dest, a, b, c, w, new_cost, flow, new_flow, u, ans;
    edge e;
    cin >> n >> m >> src >> dest;
    for(i = 0; i < m; i++)
    {
        cin >> a >> b >> c >> w;
        cap[a][b] = c;
        v[a].pb({b, w});
        v[b].pb({a, -w});
    }
    bellmanford(src);
    flow = 0;
    while(dijkstra(src, dest))
    {
        new_flow = INF;
        u = dest;
        while(u != src)
        {
            new_flow = min(new_flow, cap[p[u]][u]);
            u = p[u];
        }
        u = dest;
        while(u != src)
        {
            cap[p[u]][u] -= new_flow;
            cap[u][p[u]] += new_flow;
            u = p[u];
        }
        flow = flow + new_flow * costw[dest];
    }
    cout << flow;
}
int main()
{
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int T;
    T = 1;
    while(T--)
        solve();
    return 0;
}