#include<cstdio>
int z,y,n,m,k,j,i,l,s,d,t,w,c[351][351],p[351],h[351],r[351],g[351][351],a[351],o[351][351],b[351],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;
for(i=1;i<=n;i++)
          b[i]=10001;
b[s]=0;
for(i=1;i<=n&&!y;i++)
for(y=j=1;j<=n;j++)
for(k=0,t=g[j][0];k<a[j];t=g[j][++k])
if(c[j][t]&&b[j]+o[j][t]<b[t])
          y=0,b[t]=b[j]+o[j][t];
for(z=b[d],i=1;i<=n;i++)
for(j=0,k=g[i][0];j<a[i];k=g[i][++j])
          o[i][k]+=b[i]-b[k];
while(1)      
          {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],h[1]=h[l--],r[i]=0;
                   for(j=1;(t=2*j)<=l;j=t)
                          {if(t<l&&b[h[t+1]]<b[h[t]])
                                 t++;
                          if(b[h[j]]<=b[h[t]])
                                 break;
                          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]>0)
                          {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[t/2]];t/=2)
                                 w=h[t],h[t]=h[t/2],h[t/2]=w,r[h[t]]=t,r[h[t/2]]=t/2;}}
          if(!p[d])
                   break;
          for(m=10001,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]+z)*m;}
printf("%d",e);
return 0;}