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