#include<stdio.h>
#define N 350
int n,m,k,c[N][N],f[N][N],p,z,i,s,d,pre[N],t,l,h[N],poz[N],j,g[N][N],deg[N],o[N][N],r,w,q;
long e,b[N];
int main()
{freopen("fmcm.in","w",stdin);
freopen("fmcm.out","r",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--,g[i][deg[i]++]=j,g[j][deg[j]++]=i,o[i][j]=z,o[j][i]=-z,c[i][j]=p;}
while(1)      
          {for(t=0;t<n;t++)
                   poz[t]=-1,b[t]=3000;
          b[s]=l=0,r=3000,h[l++]=s,pre[d]=-1;
          while(l)
                   {i=h[0],poz[i]=-1,h[0]=h[--l],poz[h[0]]=t=0;
                   for(j=t?t<<1:1;j<l;j=t<<1)
                          {if(j+1<l&&b[h[j+1]]<b[h[t]])
                                   j++;
                          p=h[j],h[j]=h[t],h[t]=p,poz[h[j]]=j,poz[h[t]]=t,t=j;}
                   for(k=0;k<deg[i];k++)
                   if(c[i][g[i][k]]>f[i][g[i][k]]&&b[g[i][k]]>b[i]+o[i][g[i][k]])
                               {b[g[i][k]]=b[i]+o[i][g[i][k]],pre[g[i][k]]=i,j=poz[g[i][k]];
                               if(poz[g[i][k]]==-1)
                                      j=poz[g[i][k]]=l,h[l++]=g[i][k];
                               for(t=j>>1;t&&b[t]>b[j];t>>=1)
                                      p=h[j],h[j]=h[t],h[t]=p,poz[h[j]]=j,poz[h[t]]=t;}}
          if(pre[d]==-1)
                   break;
          for(q=d;q!=s;q=pre[q])
          if(r>c[pre[q]][q]-f[pre[q]][q])
                   r=c[pre[q]][q]-f[pre[q]][q];
          for(w=d;w!=s;w=pre[w])
                   f[pre[w]][w]+=r,f[w][pre[w]]-=r;
          e+=b[d]*r;}
printf("%ld",e);    
fclose(stdin);
fclose(stdout);
return 0;}