#include<fstream.h>
/*struct nod
{short inf;nod* adr;}*g[351];//listele de adiacenta ale grafului
inline void push(nod *&l,int x){nod *p=new nod;p->inf=x;p->adr=l;l=p;}*/
inline int min(int x,int y){return x<y?x:y;}
short n,m,s,d,heap[351],poz[351],l,t[351],cap[351][351],g[351][351];//poz - pozitia in heap, l - dimensiunea heap-ului
int dr,sc,dist[351],fl[351][351],cost[351][351];//sc - suma costurilor pe drumul de ameliorare, t - vector de tati pentru pastrarea drumului
void bf()
{int i=1,j,k,ok=1;
 for(;i<=n;++i)dist[i]=4444444;
 dist[s]=0;
 for (i=1;i<=n&&ok;++i)
 {ok=0;
  for(j=1;j<=n;++j)
   for(k=1;k<=g[j][0];++k)
	if(cap[j][g[j][k]]>0&&dist[j]+cost[j][g[j][k]]<dist[g[j][k]])
	{ok=1;
	 dist[g[j][k]]=dist[j]+cost[j][g[j][k]];}}
 sc=dist[d];}
inline void swap(short &x,short &y){short a=x;x=y;y=a;}
void perc(short k)
{while(k/2>1&&dist[heap[k]]<dist[heap[k/2]])
 {swap(heap[k],heap[k/2]);
  poz[heap[k]]=k;k/=2;
  poz[heap[k]]=k;}}
void sift(short k)
{short f;
 do  {f=k;
	  if(2*f<=l&&dist[heap[k]]>dist[heap[f*2]]) k=2*f;
	  if(2*f+1<=l&&dist[heap[k]]>dist[heap[f*2+1]]) k=2*f+1;
	  swap(heap[k],heap[f]);
	  poz[heap[k]]=k;
	  poz[heap[f]]=f;}
	  while(k!=f);}
int djk()
{int i=1,j;
 for(;i<=n;++i)
  for(j=1;j<=g[i][0];++j)
   if(dist[i]!=4444444&&dist[g[i][j]]!=4444444) cost[i][g[i][j]]+=dist[i]-dist[g[i][j]];
 for(i=1;i<=n;++i)
 {dist[i]=4444444;t[i]=-1;
  heap[i]=i;poz[i]=i;}
 dist[s]=0;l=n;
 heap[s]=1;heap[1]=s;
 poz[s]=1;poz[1]=s;
 while(l>1&&dist[heap[1]]!=4444444)
 {for(i=1;i<=g[heap[1]][0];++i)
  {j=g[heap[1]][i];
   if(cap[heap[1]][j]-fl[heap[1]][j]>0&&dist[heap[1]]+cost[heap[1]][j]<dist[j])
   {dist[j]=dist[heap[1]]+cost[heap[1]][j];
	t[j]=heap[1];
	perc(poz[j]);}}
  heap[1]=heap[l];--l;
  poz[heap[1]]=1;
  if(l>1) sift(1);}
 if(dist[d]!=4444444) 
 {j=4444444;dr=1;
  for(i=d;i!=s;i=t[i]) 
   j=min(j,cap[t[i]][i]-fl[t[i]][i]);
  for(i=d;i!=s;i=t[i]) 
   {fl[t[i]][i]+=j;
	fl[i][t[i]]-=j;}
  sc+=dist[d];
  return j * sc;}
 return 0;}
int main()
{ifstream f("fmcm.in");
ofstream h("fmcm.out");
short i,x,y,c,z;int flx=0;
f>>n>>m>>s>>d;
for (i = 1; i <= m; i++)
{f>>x>>y>>c>>z;
 g[y][++g[y][0]]=x;g[x][++g[x][0]]=y;
 cap[x][y]=c;
 cost[x][y]=z;cost[y][x]=-z;}
bf();//Bellman-Ford
do	{dr=0;
	 flx+=djk();}
while(dr);
h<<flx;
return 0;
}