#include <iostream>
#include <vector>
#include <bitset>
#include <queue>
#include <cstdio>
#define DN 3050
#define x first
#define y second
#define mp make_pair
using namespace std;

typedef pair<int,int> per;
typedef vector<per>::iterator it;

int n,a,b,s,d,cap[DN][DN],fl[DN][DN],pre[DN],dst[DN];
vector<per> gr[DN];
bitset<DN> inq;

int bf() {
  queue<int> c;
  for(int i=1; i<=n; ++i) {
    dst[i]=(1<<30); pre[i]=-1;
  }
  inq&=0;
  dst[s]=0;
  for(c.push(s);c.size(); c.pop()) {
    int fr=c.front();
    inq[fr]=0;
    for(it i=gr[fr].begin(); i!=gr[fr].end(); ++i) if(cap[fr][i->x]>fl[fr][i->x] && dst[i->x]>dst[fr]+i->y) {
      dst[i->x]=dst[fr]+i->y;
      pre[i->x]=fr;
      if(!inq[i->x]) {inq[i->x]=1; c.push(i->x);}
    }
  }
  return dst[d]!=(1<<30);
}

void add(int x,int y,int a,int b) {
  cap[x][y]=a;
  gr[x].push_back(mp(y,b));
  gr[y].push_back(mp(x,-b));
}

int main() {
  freopen("fmcm.in","r",stdin);
  freopen("fmcm.out","w",stdout);
  int m;
  cin>>n>>m>>s>>d;
  for(int i=1; i<=m; ++i) {
    int a,b,c,d;
    cin>>a>>b>>c>>d;
    add(a,b,c,d);
  }
 // cout<<"aici";
    long long cmin=0;
    for(;bf();) {
      int fc=(1<<30);
      for(int i=d; i!=s; fc=min(fc,cap[pre[i]][i]-fl[pre[i]][i]),i=pre[i]);
      for(int i=d; i!=s; fl[pre[i]][i]+=fc,fl[i][pre[i]]-=fc,i=pre[i]);
      cmin+=1LL*dst[d]*fc;
      //cerr<<cmin<<' ';
    }
    cout<<cmin<<'\n';
}