#include<stdio.h>
#include<vector.h>
#include<queue.h>
#define N 351
int n,m,k,j,i,l,s,d,c[N][N],f[N][N],p[N],h[N],r[N],g[N][N],a[N],o[N][N],b[N];
long e;
struct cmp
{bool operator()(const int &i,const int &j)
      {return b[i]>b[j];}};
priority_queue<int,vector<int>,cmp> Q;
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,m=10001,Q.push(s);
          while(!Q.empty())
                   {i=Q.top(),Q.pop(),r[i]=0;
                   for(k=0;k<a[i];k++)
                   if(b[j=g[i][k]]>b[i]+o[i][j]&&c[i][j]>f[i][j])
                           {b[j]=b[i]+o[i][j],p[j]=i;
                           if(!r[j])
                                    Q.push(j),r[j]=1;}}
          if(!p[d])
                   break;
          for(l=d;l!=s;l=p[l])
          if(m>(k=c[p[l]][l]-f[p[l]][l]))
                   m=k;
          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;}