#include<stdio.h>
#define N 351
int n,m,k,c[N][N],f[N][N],i,s,d,p[N],t,l,h[N],r[N],j,g[N][N],a[N],o[N][N],b[N],w;
long e;

void push(int x)
{int y;
while((x>>1)&&b[h[x]]<b[h[x>>1]])
          {y=h[x],h[x]=h[x>>1],h[x>>1]=y;
          r[h[x]]=x,r[h[x>>1]]=x>>1,x>>=1;}}
          
void pop(int x)
{int y=0,z;
while(x!=y)
          {y=x;
          if((y<<1)<=l&&b[h[x]]>b[h[y<<1]])
                  x=y<<1;
          if((y<<1)+1<=l&&b[h[x]]>b[h[1+(y<<1)]])
                  x=1+(y<<1);
          z=h[x],h[x]=h[y],h[y]=z;
          r[h[x]]=x,r[h[y]]=y;}}

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,m=10001,l=1;
          while(l)
                   {i=h[1],r[i]=0,h[1]=h[l--],r[h[1]]=1;
                   if(l>1)
                          pop(1);
                   for(k=0;k<a[i];k++)
                   if(b[w=g[i][k]]>b[i]+o[i][w]&&c[i][w]>f[i][w])
                          {b[w]=b[i]+o[i][w],p[w]=i;
                          if(!r[w])
                                 h[++l]=w,r[w]=l;
                          push(r[w]);}}
          if(!p[d])
                   break;
          for(l=d;l!=s;l=p[l])
          if(m>(t=c[p[l]][l]-f[p[l]][l]))
                   m=t;
          for(l=d;l!=s;l=p[l])
                   f[p[l]][l]+=m,f[l][p[l]]-=m;
          e+=b[d]*m;}
printf("%ld",e);
return 0;}