#include<stdio.h>
#define N 351
int n,m,k,j,i,l,s,d,t,q,w,c[N][N],p[N],h[N],r[N],g[N][N],a[N],o[N][N],b[N],y,z;
long e;
int main()
{freopen("fmcm.in","r",stdin);
freopen("fmcm.out","w",stdout);
scanf("%d%d%d%d",&n,&m,&s,&d);
while(m--)
          scanf("%d%d%d%d",&i,&j,&l,&k),g[i][a[i]++]=j,g[j][a[j]++]=i,o[i][j]=k,o[j][i]=-k,c[i][j]=l;
while(!z)      
          {for(i=1;i<=n;i++)
                   b[i]=10001,r[i]=0;
          b[s]=p[d]=0,h[1]=s,l=1;
          while(l)
		{
					    i=h[1],r[i]=y=0,h[1]=h[l--],r[h[1]]=1;
                         for(j=1;(t=2*j)<=l&&!y;j=t)
                          {
							  if(t<l&&b[h[t+1]]<b[h[t]])
                                 t++;
                                if(b[h[j]]<=b[h[t]])
                                 y=1;
                             else
                                 k=h[j],h[j]=h[t],h[t]=k,r[h[j]]=j,r[h[t]]=t;
						 }
                   for(k=0,j=g[i][0];k<a[i];j=g[i][++k])
                   if(b[j]>b[i]+o[i][j]&&c[i][j])
                          {
							  b[j]=b[i]+o[i][j],p[j]=i;
                                if(!r[j])
                                 h[++l]=j,r[j]=l;
                            for(t=r[j];t>3&&b[h[t]]<b[h[q=t/2]];t=q)
                                 w=h[t],h[t]=h[q],h[q]=w,r[h[t]]=t,r[h[q]]=q;
				           }
		  }
          if(!p[d])
                   z=1;
          else
                   {m=10001;
                   for(l=d;l!=s;l=p[l])
                   if(m>c[p[l]][l])
                           m=c[p[l]][l];
                   for(l=d;l!=s;l=p[l])
                           c[p[l]][l]-=m,c[l][p[l]]+=m;
                   e=e+b[d]*m;}}
printf("%ld",e);
return 0;}