#include<fstream.h>
#include<string.h>
#include<stdlib.h>
#define nx 352
#define mx 800000
int inf=2000000000;
int cap[nx][nx],flux[nx][nx],drum;
int n,m,tat[nx],*a[nx],cost[nx][nx],d[nx],Q[mx],S,D,inQ[nx];
inline int min(int a,int b)
 {
  if (a<b) return a;
  return b;
 }

int bf ()
 {
  int i,w,nod,r,st,dr;
  memset(inQ,0,sizeof(inQ));
  for (i=1;i<=n;++i)
   d[i]=inf;
  Q[1]=S;d[S]=0;inQ[S]=1;
  st=dr=1;
  while (st<=dr)
   {
    nod=Q[st++];
    inQ[nod]=0;
    for (i=1;i<=a[nod][0];++i)
     {
      w=a[nod][i];
      if (cap[nod][w]>flux[nod][w] && d[w]>d[nod]+cost[nod][w])
       {
	d[w]=d[nod]+cost[nod][w];
	tat[w]=nod;
	if (!inQ[w])
	 {
	  inQ[w]=1;
	  Q[++dr]=w;
	 }
       }
     }
   }
  if (d[D]!=inf)
   {
    drum=1;
    r=inf;
    for (i=D;i!=S;i=tat[i])
     r=min(r,cap[tat[i]][i]-flux[tat[i]][i]);
    for (i=D;i!=S;i=tat[i])
     {
      flux[tat[i]][i]+=r;
      flux[i][tat[i]]-=r;
     }
    return d[D]*r;
   }
  return 0;
 }

int fluxx()
 {
  int r,rez=0;drum=1;
  while (drum)
   {
    drum=0;
    rez+=bf();
   }
  return rez;
 }

int main()
 {
  ifstream be ("maxflow.in");
  ofstream ki ("maxflow.out");
  be>>n>>m>>S>>D;
  int i,x,y,z,c;
  for (i=1;i<=n;++i)
   {
    a[i]=(int*)realloc(a[i],sizeof(int));
    a[i][0]=0;
   }
  for (i=1;i<=m;++i)
   {
    be>>x>>y>>z>>c;
    cap[x][y]=z;
    cost[x][y]=c;
    cost[y][x]=-c;
    a[x][0]++;
    a[x]=(int*)realloc(a[x],(a[x][0]+1)*sizeof(int));
    a[x][a[x][0]]=y;
    a[y][0]++;
    a[y]=(int*)realloc(a[y],(a[y][0]+1)*sizeof(int));
    a[y][a[y][0]]=x;
   }
  be.close();
  ki<<fluxx()<<'\n';
  ki.close();
  return 0;
 }