#include<fstream.h>
#include<string.h>
#include<stdlib.h>
#define nx 355
#define mx 800000
#define inf 2000000000
int cap[nx][nx],flux[nx][nx],drum;
int n,m,tat[nx],a[nx][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,r,st,dr;
  for (i=1;i<=n;++i)
   {d[i]=inf;
   tat[i]=-1;
   inQ[i]=0;}
  Q[1]=S;d[S]=0;inQ[S]=1;
  st=dr=1;
  while (st<=dr)
   {
    r=Q[st++];
    inQ[r]=0;
    for (int *v=a[r];*v;v++)
      if (cap[r][*v]>flux[r][*v] && d[*v]>d[r]+cost[r][*v])
       {
	d[*v]=d[r]+cost[r][*v];
	tat[*v]=r;
	if (!inQ[*v])
	 {
	  inQ[*v]=1;
	  Q[++dr]=*v;
	 }
       }
   }
  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;
 }

long fluxx()
 {
  long rez=0;drum=1;
  while (drum)
   {
    drum=0;
    rez+=bf();
   }
  return rez;
 }

int main()
 {
  ifstream be ("fmcm.in");
  ofstream ki ("fmcm.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;
 }