#include <fstream>
#include <string.h>
#include <stdlib.h>
#define nmax 355
#define mmax  12505
#define inf 125050000
using namespace std;
fstream f1("fmcm.in", ios::in);
fstream f2("fmcm.out", ios::out);
int n, m, s, d, ok=1;
int aux[nmax], cap[nmax], cost[nmax][nmax], ca[nmax][nmax], v[mmax*2], viz[nmax], coada[nmax], prim, ultim, k, pred[nmax];
long int dist[nmax], fmax;
struct muchii
{
    int x, y;
}muc[mmax];
void citire()
{
    int x, y, c, i,CA;
    f1>>n>>m>>s>>d;
    for(i=1; i<=m; i++)
    {
        f1>>muc[i].x>>muc[i].y>>CA>>c;
        aux[muc[i].x]++;
        aux[muc[i].y]++;
        cost[muc[i].x][muc[i].y]=c;
        cost[muc[i].y][muc[i].x]=-c;
        ca[muc[i].x][muc[i].y]=CA;
    }
    cap[1]=1;
    for(i=2; i<=n+1; i++)
    {
        cap[i]=cap[i-1]+aux[i-1];
        aux[i-1]=cap[i-1];
    }
    for(i=1; i<=m; i++)
    {
        x=muc[i].x;
        y=muc[i].y;
        v[aux[x]]=y;
        aux[x]++;
        v[aux[y]]=x;
        aux[y]++;
    }
}
void init()
{
    memset(viz, 0, sizeof(viz));
    memset(pred, 0, sizeof(pred));
    for(int i=1; i<=n; i++)
        dist[i]=inf;
    prim=1;
    ultim=1;
    k=1;
    coada[prim]=s;
    viz[s]=1;
    dist[s]=0;
}
void bellman()
{
    int nod, vec, i;
    while(k!=0)
    {
        nod=coada[prim];
        viz[nod]=0;
        prim++;
        k--;

        for(i=cap[nod]; i<cap[nod+1]; i++)
        {
            vec=v[i];
            if((ca[nod][vec]>0)&&(dist[vec]> dist[nod]+cost[nod][vec]))
            {
                dist[vec]= dist[nod]+cost[nod][vec];
                pred[vec]=nod;
                if(!viz[vec])
                {
                    viz[vec]=1;
                    ultim++;
                    k++;
                    coada[ultim]=vec;
                }
            }
        }
    }
    if(dist[d]!=inf)  ok=1;
    else ok=0;
}
void actual()
{
  int nod;
  long int fmin=inf;

  nod=d;
  while(pred[nod])
  {
      if(fmin> ca[pred[nod]][nod]) fmin= ca[pred[nod]][nod];
      nod=pred[nod];
  }

  nod=d;
  while(pred[nod])
  {
      ca[pred[nod]][nod]-=fmin;
      ca[nod][pred[nod]]+=fmin;
      nod=pred[nod];
  }

  fmax+=dist[d]*fmin;
}
int main()
{
    citire();
    while(1)
       {
           init();
           bellman();
           if(ok) actual();
           else break;
       }
   f2<<fmax;
    return 0;
}