///mr robot
#include <bits/stdc++.h>

using namespace std;

const int Nmax = 350 + 10;
const int inf = 0x3f3f3f3f;

int n , m , S , D , i , flow;
int dad[Nmax] , bst[Nmax];
int c[Nmax][Nmax] , f[Nmax][Nmax] , p[Nmax][Nmax];

vector < int > g[Nmax];
queue < int > q;

bool marked[Nmax];

bool bfs()
{
    memset(bst , inf , sizeof(bst));
    memset(marked , 0 , sizeof(marked));
    memset(dad , 0 , sizeof(dad));

    for (q.push(S),bst[S]=0,marked[S]=1; !q.empty(); q.pop())
    {
        int node = q.front(); marked[node] = 0;
        for (auto &it : g[node])
        {
            if (bst[it] > bst[node] + p[node][it] && c[node][it] > f[node][it])
            {
                bst[it] = bst[node] + p[node][it];
                dad[it] = node;

                if (!marked[it]) marked[it] = 1, q.push(it);
            }
        }
    }

    return dad[D];
}

void fluxx()
{
    for (bool ok = bfs() ; ok ; ok = bfs())
    {
        int minn = inf;
        for (int node = D; node != S; node = dad[node])
            minn = min(minn , c[dad[node]][node] - f[dad[node]][node]);

        flow += minn * bst[D];
        for (int node = D; node != S; node = dad[node])
            f[dad[node]][node] += minn,
            f[node][dad[node]] -= minn;
    }
}

int main()
{
    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);

    scanf("%d %d %d %d", &n, &m, &S, &D);

    for (i = 1; i <= m; ++i)
    {
        int node1, node2, capacitate , cost;
        scanf("%d %d %d %d", &node1, &node2, &capacitate , &cost);

        g[node1].push_back(node2); g[node2].push_back(node1);
        c[node1][node2] = capacitate;
        p[node1][node2] = cost; p[node2][node1] = cost * (-1);
    }

    fluxx();
    printf("%d\n", flow);

    return 0;
}