#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}


template<typename TF,typename TC>
struct PrimalDual{
  struct edge{
    int to;
    TF cap;
    TC cost;
    int rev;
    edge(){}
    edge(int to,TF cap,TC cost,int rev):
      to(to),cap(cap),cost(cost),rev(rev){}
  };

  static const TC INF;
  vector<vector<edge>> G;
  vector<TC> h,dist;
  vector<int> prevv,preve;

  PrimalDual(){}
  PrimalDual(int n):G(n),h(n),dist(n),prevv(n),preve(n){}

  void add_edge(int u,int v,TF cap,TC cost){
    G[u].emplace_back(v,cap,cost,G[v].size());
    G[v].emplace_back(u,0,-cost,G[u].size()-1);
  }

  void dijkstra(int s){
    struct P{
      TC first;
      int second;
      P(TC first,int second):first(first),second(second){}
      bool operator<(const P&a) const{return a.first<first;}
    };
    priority_queue<P> que;
    fill(dist.begin(),dist.end(),INF);

    dist[s]=0;
    que.emplace(dist[s],s);
    while(!que.empty()){
      P p=que.top();que.pop();
      int v=p.second;
      if(dist[v]<p.first) continue;
      for(int i=0;i<(int)G[v].size();i++){
        edge &e=G[v][i];
        if(e.cap==0) continue;
        if(dist[v]+e.cost+h[v]-h[e.to]<dist[e.to]){
          dist[e.to]=dist[v]+e.cost+h[v]-h[e.to];
          prevv[e.to]=v;
          preve[e.to]=i;
          que.emplace(dist[e.to],e.to);
        }
      }
    }
  }

  TC flow(int s,int t,TF f,int &ok){
    TC res=0;
    fill(h.begin(),h.end(),0);
    while(f>0){
      dijkstra(s);
      if(dist[t]==INF){
        ok=0;
        return res;
      }

      for(int v=0;v<(int)h.size();v++)
        if(dist[v]<INF) h[v]=h[v]+dist[v];

      TF d=f;
      for(int v=t;v!=s;v=prevv[v])
        d=min(d,G[prevv[v]][preve[v]].cap);

      f-=d;
      res=res+h[t]*d;
      for(int v=t;v!=s;v=prevv[v]){
        edge &e=G[prevv[v]][preve[v]];
        e.cap-=d;
        G[v][e.rev].cap+=d;
      }
    }
    ok=1;
    return res;
  }
};
template<typename TF, typename TC>
const TC PrimalDual<TF, TC>::INF = numeric_limits<TC>::max()/2;


template<typename TF,typename TC>
struct NegativeEdge{
  PrimalDual<TF, TC> G;
  vector<TF> fs;
  TC sum;
  int S,T;
  NegativeEdge(){}
  NegativeEdge(int n):G(n+2),fs(n+2,0),sum(0),S(n),T(n+1){}

  void use_edge(int u,int v,TF cap,TC cost){
    fs[u]-=cap;
    fs[v]+=cap;
    sum=sum+cost*cap;
  }

  void add_edge(int u,int v,TF cap,TC cost){
    if(cost<TC(0)){
      use_edge(u,v,cap,cost);
      swap(u,v);
      cost=-cost;
    }
    G.add_edge(u,v,cap,cost);
  }

  TC flow(int &ok){
    TF f=0;
    for(int i=0;i<S;i++){
      if(fs[i]>0){
        f+=fs[i];
        G.add_edge(S,i,+fs[i],TC(0));
      }
      if(fs[i]<0){
        G.add_edge(i,T,-fs[i],TC(0));
      }
    }
    return sum+G.flow(S,T,f,ok);
  }

  TC flow(int ts,int tt,TF tf,int &ok){
    fs[ts]+=tf;
    fs[tt]-=tf;
    return flow(ok);
  }
};


template<typename T>
struct BellmanFord{
  static constexpr T INF = numeric_limits<T>::max();

  struct edge{
    int u,v;
    T w;
    edge(){}
    edge(int u,int v,T w):u(u),v(v),w(w){}
  };

  int n;
  vector< vector<int> > G;
  vector<int> used,reach;
  BellmanFord(int n):n(n),G(n),used(n,0),reach(n,1){}

  vector<edge> es;
  void add_edge(int u,int v,T c){
    es.emplace_back(u,v,c);
    G[u].emplace_back(v);
  }

  vector<T> build(int from,int &neg_loop){
    vector<T> ds(n,INF);
    ds[from]=0;
    for(int j=0;j<n;j++){
      bool update=0;
      for(auto e:es){
        if(!reach[e.u]||!reach[e.v]||ds[e.u]==INF) continue;
        if(ds[e.v]>ds[e.u]+e.w){
          ds[e.v]=ds[e.u]+e.w;
          update=1;
        }
      }
      if(!update) break;
      if(j==n-1){
        neg_loop=1;
        return ds;
      }
    }
    neg_loop=0;
    return ds;
  }

  void dfs(int v){
    if(used[v]) return;
    used[v]=1;
    for(int u:G[v]) dfs(u);
  }

  T shortest_path(int from,int to,int &neg_loop){
    for(int i=0;i<n;i++){
      fill(used.begin(),used.end(),0);
      dfs(i);
      reach[i]=used[to];
    }
    return build(from,neg_loop)[to];
  }
};
template<typename T>
constexpr T BellmanFord<T>::INF;

//INSERT ABOVE HERE
signed main(){
  using ll = long long;
  const ll INF = 1e9;
  int n,m,s,t;
  cin>>n>>m>>s>>t;
  s--;t--;
  NegativeEdge<ll, ll> G(n);
  BellmanFord<int> H(n);
  for(int i=0;i<m;i++){
    int u,v,d,c;
    cin>>u>>v>>d>>c;
    u--;v--;
    G.add_edge(u,v,c,d);
    H.add_edge(u,v,d);
  }
  int neg_loop;
  int len=H.shortest_path(s,t,neg_loop);
  assert(!neg_loop);
  G.add_edge(t,s,INF,-(len+1));
  int ok;
  cout<<-G.flow(ok)<<endl;
  assert(ok);
  return 0;
}



Measured memory_bytes: 3332