#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;

template <class T>
bool ReadNr(T &_value) {
  bool _sign = 0;
  char ch;
  _value = 0;
  while(!isdigit(ch = getchar())) {
    if (ch == -1) return false;
    _sign = (ch == '-');
  }
  do { _value = _value * 10 + (ch - '0');
  } while(isdigit(ch = getchar()));
  _value = _sign ? -_value : _value;
  return true;
}


typedef struct lnod {
    int nod,cost,cap,flow,last;
}nod;

const int INF=1e9+69*69;

int i,n,m,flow,rs,start,fin,x,y,cap,cost;
int q[355],tata[355],d[355],id[355],qh,qt,poz[355];
vector<nod> g[355];

void add(int x,int y,int cap,int cost) {
    nod r1={y,cost,cap,0,(int)g[y].size()};
    nod r2={x,-cost,0,0,(int)g[x].size()};

    g[x].push_back(r1);
    g[y].push_back(r2);
}

int Update() {
    int addflow=INF;

    for(x=fin;x!=start;x=tata[x])
    {
      int p=tata[x],pos=poz[x];
      addflow=min(addflow,g[p][pos].cap-g[p][pos].flow);
    }

    for(x=fin;x!=start;x=tata[x])
    {
      int p=tata[x],pos=poz[x];
      int rev=g[p][pos].last;

      g[p][pos].flow+=addflow;
      g[x][rev].flow-=addflow;
      rs+=g[p][pos].cost*addflow;
    }

    return addflow;
}

int main()
{
  freopen("fmcm.in", "r", stdin);
  freopen("fmcm.out", "w", stdout);

  ReadNr(n); ReadNr(m); ReadNr(start); ReadNr(fin);
  for(; m; --m) {
    ReadNr(x); ReadNr(y); ReadNr(cap); ReadNr(cost);
    add(x,y,cap,cost);
  }

  while(1) {
    for(i=0;i<=n+1;++i) id[i]=0,d[i]=INF;

    qh=qt=0; q[qt++]=start; d[start]=0;

    while(qh!=qt)
    {
      x=q[qh++]; id[x]=2;
      if(qh==n) qh=0;

      for(i=0;i<(int)g[x].size();++i)
      {
        nod &r=g[x][i];
        if(r.flow<r.cap && d[r.nod]>d[x]+r.cost)
        {
          d[r.nod]=d[x]+r.cost;

          if(!id[r.nod])
          {
            q[qt++]=r.nod;
            if(qt==n) qt=0;
          }
          else if(id[r.nod]==2)
               {
                 if(--qh==-1) qh=n-1;
                 q[qh]=r.nod;
               }

          id[r.nod]=1; tata[r.nod]=x; poz[r.nod]=i;
        }
      }
    }

    if(d[fin]==INF) break;

    flow+=Update();
  }

  printf("%d\n", rs);

 return 0;
}