#include<stdio.h>
#define INF 30001
#define N 351
#define XS(a,b) a^=b^=a^=b
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]={0},o[N][N],r,b[N];
long e=0;
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--;
          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(k=0;k<n;k++)
                   pre[k]=poz[k]=-1,b[k]=INF;
          b[s]=poz[s]=l=j=0,m=INF,h[l++]=s;
          while(l)
                   {i=h[0],poz[i]=-1,h[0]=h[--l],poz[h[0]]=t=0;
                   while(1)
                               {if(t)
                                      j=t<<1;
                               else
                                      j=1;
                               if(j+1<l&&b[h[j+1]]<b[h[t]])
                                      j++;
                               else 
                                      if(j>=l)
                                              break;
                               if(t!=j)
                                      XS(poz[h[j]],poz[h[t]]),XS(h[j],h[t]);
                               t=j,j=t<<1;}
                   for(k=0;k<deg[i];k++)
                               {r=g[i][k];
                               if(c[i][r]>f[i][r]&&b[r]>b[i]+o[i][r])
                                       {b[r]=b[i]+o[i][r];
                                       pre[r]=i;
                                       if(poz[r]==-1)
                                             {poz[r]=l,h[l++]=r,j=poz[r];
                                             for(t=j>>1;t&&b[t]>b[j];j>>=1,t=j>>1)
                                                     XS(poz[h[j]],poz[h[t]]),XS(h[j],h[t]);}}}}
          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+=b[d]*m;}
printf("%ld",e);
fclose(stdin);
fclose(stdout);
return 0;}