#include <algorithm>
#include <vector>
#include <bitset>
#include <queue>
using namespace std;

#define INF 0x3f3f3f3f
#define pb push_back
#define mp make_pair
#define sc second
#define fs first
#define DIM 355

vector <pair <int,int> > g[DIM];
int c[DIM][DIM],f[DIM][DIM];
int dst[DIM],t[DIM];
bitset <DIM> viz;
int n,m,s,d,cost;

struct cmp
{
    bool operator () (const int &a,const int &b) const
    {
        return dst[a]>dst[b];
    }
}; priority_queue <int,vector <int>,cmp> q;

void read ()
{
    int i,x,y,z,w;

    scanf ("%d%d%d%d",&n,&m,&s,&d);
    for (i=1; i<=m; ++i)
    {
        scanf ("%d%d%d%d",&x,&y,&z,&w);
        c[x][y]=z;
        g[x].pb (mp (y,w));
        g[y].pb (mp (x,-w));
    }
}

int dijkstra ()
{
    vector <pair <int,int> > :: iterator it;
    int nod,i;

    memset (dst,INF,sizeof (dst));
    dst[s]=0;
    for (q.push (s); !q.empty (); )
    {
        viz[nod=q.top ()]=0; q.pop ();
        for (it=g[nod].begin (); it!=g[nod].end (); ++it)
            if (dst[it->fs]>dst[nod]+it->sc && c[nod][it->fs]>f[nod][it->fs])
            {
                dst[it->fs]=dst[nod]+it->sc;
                t[it->fs]=nod;
                if (!viz[it->fs])
                {
                    q.push (it->fs);
                    viz[it->fs]=1;
                }
            }
    }
    if (dst[d]==INF)
        return 0;
    return 1;
}

void solve ()
{
    int nrmin,i;

    for (nrmin=INF; dijkstra (); nrmin=INF)
    {
        for (i=d; i!=s; i=t[i])
            nrmin=min (nrmin,c[t[i]][i]-f[t[i]][i]);
        for (i=d; i!=s; i=t[i])
        {
            f[t[i]][i]+=nrmin;
            f[i][t[i]]-=nrmin;
        }
        cost+=nrmin*dst[d];
    }
    printf ("%d",cost);
}

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

    read ();
    solve ();

    return 0;
}