#include <stdio.h>

#define DIM 355
#define oo 10005

struct nod {int x;
            nod *urm;} *lst[DIM];
int c[DIM][DIM],f[DIM][DIM],ct[DIM][DIM];
int q[DIM*DIM],viz[DIM],t[DIM],dist[DIM];
int n,m,s,d,minim;
long long cost;

void add (int x,int y)
{
    nod *p=new nod;

    p->x=x;
    p->urm=lst[y];
    lst[y]=p;
}

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

    scanf ("%d%d%d%d",&n,&m,&s,&d);
    for (i=1; i<=m; ++i)
    {
        scanf ("%d%d%d%d",&x,&y,&z,&t);
        add (x,y);
        add (y,x);
        c[x][y]=z;
        ct[x][y]=t;
        ct[y][x]=-t;
    }
}

int bellman_ford ()
{
    int st,dr;
    nod *p;

    for (dist[q[st=dr=1]=s]=0; st<=dr; ++st)
    {
        for (p=lst[q[st]]; p; p=p->urm)
            if (c[q[st]][p->x]>f[q[st]][p->x] && dist[q[st]]+ct[q[st]][p->x]<dist[p->x])
            {
                dist[p->x]=dist[q[st]]+ct[q[st]][p->x];
                t[p->x]=q[st];
                if (!viz[p->x])
                    viz[q[++dr]=p->x]=1;
            }
        viz[q[st]]=0;
    }
    if (dist[d]!=oo)
        return 1;
    return 0;
}

void init ()
{
    int i;

    for (i=1; i<=n; ++i)
    {
        t[i]=viz[i]=0;
        dist[i]=oo;
    }
}

int min (int a,int b)
{
    if (a<b)
        return a;
    return b;
}

void solve ()
{
    int i;

    for (minim=oo; bellman_ford (); init ())
    {
        for (i=d; i!=s; i=t[i])
            minim=min (minim,c[t[i]][i]-f[t[i]][i]);
        for (i=d; i!=s; i=t[i])
        {
            f[t[i]][i]+=minim;
            f[i][t[i]]-=minim;
        }
        cost+=minim*dist[d];
    }
    printf ("%lld",cost);
}

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

    read ();
    solve ();

    return 0;
}