#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define N 355
#define oo 1<<30

using namespace std;
vector<int>v[N];
int tata[N], fl[N][N], cost[N][N], cap[N][N], i, db[N], dd[N], dr[N], n, x, y, co, ca, s, d, nod, m, minflow, sol;
deque<int>q;
bitset<N>inq;
priority_queue<pii, vector<pii>, greater<pii>>pq;

void bellman()
{
    for(i = 1; i <= n; i++)
        db[i] = oo;
    db[s] = 0;
    q.pb(s);
    inq[s] = 1;
    while(q.size())
    {
        nod = q.front();
        q.pop_front();
        inq[nod] = 0;
        for(auto it : v[nod])
        {
            if(db[it] > db[nod] + cost[nod][it] && fl[nod][it] < cap[nod][it])
            {
                db[it] = db[nod] + cost[nod][it];
                if(!inq[it])
                {
                    inq[it] = 1;
                    q.pb(it);
                }
            }
        }
    }
}
bool dijkstra()
{
    for(i = 1; i <= n; i++)
        dd[i] = oo;
    dd[s] = 0;
    tata[s] = s;
    pq.push(mp(0, s));
    while(pq.size())
    {
        nod = pq.top().second;
        if(pq.top().first>dd[nod])
            continue;
        pq.pop();
        for(auto it : v[nod])
        {
            if(dd[it] > dd[nod] + cost[nod][it] + db[nod] - db[it] && fl[nod][it] < cap[nod][it])
            {
                dd[it] = dd[nod]+cost[nod][it] + db[nod] - db[it];
                dr[it] = dr[nod] + cost[nod][it];
                tata[it] = nod;
                pq.push(mp(dd[it], it));
            }
        }
    }
    for(i = 1; i <= n; i++)
        db[i] = dr[i];
    return dd[d] != oo;
}
int main()
{
    freopen("fmcm.in", "r", stdin);
    freopen("fmcm.out", "w", stdout);
    scanf("%d%d%d%d", &n, &m, &s, &d);
    for(; m; m--)
    {
        scanf("%d%d%d%d", &x, &y, &ca, &co);
        v[x].pb(y);
        v[y].pb(x);
        cost[x][y] = co;
        cost[y][x] = -co;
        cap[x][y] = ca;
    }
    bellman();
    while(dijkstra())
    {
        minflow = oo;
        for(x = d; x != tata[x]; x = tata[x])
            minflow = min(minflow, cap[tata[x]][x] - fl[tata[x]][x]);
        for(x = d; x != tata[x]; x = tata[x])
        {
            fl[tata[x]][x] += minflow;
            fl[x][tata[x]] -= minflow;
        }
        sol += db[d] * minflow;
    }
    printf("%d\n", sol);
    return 0;
}