#include<stdio.h>
#define N 350
int n,m,k,c[N][N],f[N][N],i,s,d,p[N],t,l,h[N],r[N],j,g[N][N],a[N],o[N][N],b[N],q;
long e;
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,&l,&k),i--,j--,g[i][a[i]++]=j,g[j][a[j]++]=i,o[i][j]=k,o[j][i]=-k,c[i][j]=l;
while(1)      
          {for(i=0;i<n;i++)
                   b[i]=10001,r[i]=-1;
          b[s]=0,h[0]=s,m=10001,l=1,p[d]=-1;
          while(l)
                   {i=h[0],r[i]=-1,h[0]=h[--l],r[h[0]]=j=k=0;
                   while(k<l)
                          {if(k+1<l&&b[h[k+1]]<b[h[k]])
                                 k++;
                          if(b[h[j]]<=b[h[k]])
                                 break;
                          h[j]^=h[k]^=h[j]^=h[k],r[h[j]]=j,r[h[k]]=j=k,k<<=1;}
                   for(k=0;k<a[i];k++)
                   if(c[i][j=g[i][k]]>f[i][j]&&b[j]>b[i]+o[i][j])
                          {b[j]=b[i]+o[i][j],p[j]=i,q=r[j];
                          if(q<0)
                                 q=r[j]=l,h[l++]=j;
                          while(b[h[t=q>>1]]>b[h[q]])
                                 h[q]^=h[t]^=h[q]^=h[t],r[h[q]]=q,r[h[t]]=t,q=t;}}
          if(p[d]<0)
                   break;
          for(l=d;l!=s;l=p[l])
          if(m>(t=c[p[l]][l]-f[p[l]][l]))
                   m=t;
          for(l=d;l!=s;l=p[l])
                   f[p[l]][l]+=m,f[l][p[l]]-=m;
          e+=b[d]*m;}
printf("%ld",e);
return 0;}