#include<fstream.h>
#include<vector.h>
#include<queue.h>
#define N 351
int n,m,k,j,i,s,d,l,c[N][N],f[N][N],p[N],r[N],g[N][N],a[N],o[N][N],b[N];
long e;
struct cmp
{bool operator()(int i,int j)
      {return b[i]>b[j];}};
priority_queue<int,vector<int>,cmp> Q;
int main()
{ifstream f1("fmcm.in");
ofstream f2("fmcm.out");
f1>>n>>m>>s>>d;
while(m--)
          f1>>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(i=d;i!=s;i=p[i])
          if(m>(k=c[p[i]][i]-f[p[i]][i]))
                   m=k;
          for(i=d;i!=s;i=p[i])
                   f[p[i]][i]+=m,f[i][p[i]]-=m;
          e+=b[d]*m;}
f2<<e;
return 0;}