#include<stdio.h>
#define INF 30001
#define N 351
typedef struct nod
{long cost,vecin;
struct nod *urm;}Nod;
int n,m,k,c[N][N],f[N][N],p,z,i,s,d,pre[N],t,l,h[N],poz[N],j;
long e=0,b[N];
Nod *a[N],*q;

void Down(int t)
{int i,k;
for(i=t?t<<1:1;;i=t<<1)
      {if(i+1<l&&b[h[i+1]]<b[h[t]])
             i++;
      else 
             if(i>=l)
                    return;
      k=poz[h[i]];
      poz[h[i]]=poz[h[t]];
      poz[h[t]]=k;
      k=h[i];
      h[i]=h[t];
      h[t]=k;
      t=i;}}

int Pop()
{int i=h[0];
poz[i]=-1;
h[0]=h[--l];
poz[h[0]]=0;
Down(0);
return i;}

void Up(int i)
{int t,k;
for(t=i>>1;i&&b[t]>b[i];i>>=1,t=i>>1)
      {k=poz[h[i]];
      poz[h[i]]=poz[h[t]];
      poz[h[t]]=k;
      k=h[i];
      h[i]=h[t];
      h[t]=k;}}

void Push(int i,long  dist)
{b[i]=dist;
if(poz[i]==-1)
      {poz[i]=l;
      h[l++]=i;
      Up(poz[i]);}}
      
void add(int i,int j,int k)
{Nod *t=new Nod;
t->vecin=j;
t->cost=k;
t->urm=a[i];
a[i]=t;}

int main()
{freopen("fmcm.in","r",stdin);
freopen("fmcm.out","w",stdout);
scanf("%d%d%d%d",&n,&m,&s,&d);
s--,d--;
while(m--)
          {scanf("%d%d%d%d",&i,&j,&p,&z);
          i--,j--;
          add(i,j,z);
          add(j,i,-z);
          c[i][j]=p;}
while(1)      
          {for(i=0;i<n;i++)
                   pre[i]=poz[i]=-1,b[i]=INF;
          l=0,m=INF;
          Push(s,0);
          while(l)
                   {i=Pop();
                   for(q=a[i];q;q=q->urm)
                   if(f[i][q->vecin]<c[i][q->vecin]&&b[q->vecin]>b[i]+q->cost)
                               {b[q->vecin]=b[i]+q->cost;
                               pre[q->vecin]=i;
                               Push(q->vecin,b[q->vecin]);}}
          if(pre[d]==-1)
                   break;
          for(l=d;l!=s;l=pre[l])
          if(m>(t=c[pre[l]][l]-f[pre[l]][l]))
                   m=t;
          for(l=d;l!=s;l=pre[l])
                   f[pre[l]][l]+=m,f[l][pre[l]]-=m;
          e=e+b[d]*m;}
printf("%ld",e);    
fclose(stdin);
fclose(stdout);
return 0;}