#include <stdio.h>
#define Lg 355

using namespace std;

struct nod
{
     int inf;
     nod *next;
}*sir[Lg];

int cap[Lg][Lg],cost[Lg][Lg];
int n,m,S,D,rez,inc,sf,Cost_aux;
int Q[Lg*Lg],tati[Lg],Cost[Lg];
char viz[Lg];


void adauga(int a,int b)
{
     nod *q=new nod;
     q->inf=b;
     q->next=sir[a];
     sir[a]=q;
}

void citire()
{
     freopen ("fmcm.in","r",stdin);
     freopen ("fmcm.out","w",stdout);

     int x,y,c,cos;
     scanf ("%d %d %d %d\n",&n,&m,&S,&D);
     for (int i=0;i<m;i++)
     {
          scanf ("%d %d %d %d\n",&x,&y,&c,&cos);
          adauga(x,y);
          adauga(y,x);
          cap[x][y]=c;
          cost[x][y]=cos;
          cost[y][x]=-cos;
     }
}

void bell_BMW()
{
     int N,N1;
     for (int  i=1;i<=n;i++)
          Cost[i]=6000000LL;
     inc=0;
     sf=1;
     Q[inc]=S;
     Cost[S]=0;
     viz[S]=1;
     while (inc<sf)
     {
          N=Q[inc++];
          viz[N]=0;
          Cost_aux=Cost[N];
          for (nod *q=sir[N];q;q=q->next)
          {
               N1=q->inf;
               if (cap[N][N1] && Cost[N1]>Cost_aux+cost[N][N1])
               {
                    Cost[N1]=Cost_aux+cost[N][N1];
                    tati[N1]=N;
                    if (!viz[N1])
                    {
                         viz[N1]=1;
                         Q[sf++]=N1;
                    }
               }
          }
     }
}

void fmcm()
{
     int flux,poz,T;
     bell_BMW();
     while (Cost[D]!=6000000LL)
     {
          flux=6000000LL;
          poz=D;
          while (poz!=S)
          {
               T=tati[poz];
               flux=(flux>cap[T][poz])?cap[T][poz]:flux;
               poz=T;
          }

          poz=D;
          while (poz!=S)
          {
               T=tati[poz];
               cap[T][poz]-=flux;
               cap[poz][T]+=flux;
               poz=T;
          }
          rez+=flux*Cost[D];
          bell_BMW();
     }
}

int main ()
{
     citire();
     fmcm();
     printf("%d\n",rez);
     return 0;
}