#include <cstdio>
#include <vector>
#include <cstring>
#define MaxN 355
#define MAX 1000005
#define Inf 2000000000
#define infile "fmcm.in"
#define outfile "fmcm.out"

using namespace std;

vector <int> G[MaxN];

int cap[MaxN][MaxN],cost[MaxN][MaxN],b[MaxN][MaxN];
int t[MaxN],Q[MAX],uz[MaxN],dist[MaxN];
int N,M,S,D,sw=1,MIN;
long long CT;

void add(int x,int y)
{
      G[x].push_back(y);
}

void read()
{
      int i,x,y,c,z;
      scanf("%d%d%d%d",&N,&M,&S,&D);
      for(i=1;i<=M;i++)
      {
            scanf("%d%d%d%d",&x,&y,&c,&z);
            add(x,y); add(y,x);
            cap[x][y]=c; cost[x][y]=z;
            cost[y][x]=-z;
      }
}

void BF()
{
      int i,p=1,j,x,nr,y;
      for(i=1;i<=N;i++)
            dist[i]=Inf, t[i]=-1;
     sw=0;
     dist[S]=0;

     Q[p]=S; uz[S]=1;
     for(i=1;i<=p;i++)
     {
            x=Q[i]; nr=G[x].size();
            for(j=0;j<nr;j++)
            {
                  y=G[x][j];
                  if(cap[x][y]-b[x][y]>0 && dist[x]+cost[x][y]<dist[y])
                        {
                              dist[y]=dist[x]+cost[x][y];
                              t[y]=x;
                              if(!uz[y])
                              {
                                    Q[++p]=y;
                                    uz[y]=1;
                              }
                        }
            }
            uz[x]=0;
     }

     if(dist[D]!=Inf)
            sw=1;
}



void solve()
{
      int nod;
      do{
            BF();
            if(sw)
            {
                  MIN=Inf;
                  nod=D;
                  while(nod!=S)
                  {
                        if(cap[t[nod]][nod]-b[t[nod]][nod]<MIN)
                              MIN=cap[t[nod]][nod]-b[t[nod]][nod];
                        nod=t[nod];
                  }
                  nod=D;
                  while(nod!=S)
                  {
                        b[t[nod]][nod]+=MIN;
                        b[nod][t[nod]]-=MIN;
                        CT+=(long long)(cost[t[nod]][nod]*MIN);
                        nod=t[nod];
                  }
            }

      }while(sw);
}

void write()
{
      printf("%lld\n",CT);
}

int main()
{
      freopen(infile,"r",stdin);
      freopen(outfile,"w",stdout);

      read();
      solve();
      write();

      fclose(stdin);
      fclose(stdout);
      return 0;
}