#include <fstream>
#include <vector>
#include <bitset>
#include <queue>
#define ll long long
#define st first
#define nd second
#define PII pair<int,int>

using namespace std;

ifstream fin("fmcm.in");
ofstream fout("fmcm.out");

const int MAXN = 355 , INF = int(2e9);
vector<PII> G[MAXN];
int S , D , N ,  M , drum;
int Dist[MAXN] , C[MAXN][MAXN] , F[MAXN][MAXN] , TT[MAXN];
bitset<MAXN> u;

struct cmp { bool operator() (const int &x,const int &y)
	const { return &Dist[x] > &Dist[y]; }
};

priority_queue<int,vector<int>,cmp > Q;

void read_data()
{
	int x , y , cap ,z;
	for(fin>>N>>M>>S>>D;M;M--)
	{
		fin>>x>>y>>cap>>z;
		G[x].push_back(make_pair(y,z));
		G[y].push_back(make_pair(x,-z));
		C[x][y] = cap;
	}
}

int bellmanford()
{
	int v , fmin = INF;
	fill(Dist+1,Dist+N+1,INF);
	u.reset();
	Dist[S] = 0; u[S] = 1;
	Q.push(S);
	while(!Q.empty())
	{
		v = Q.top() , Q.pop();
		for(vector<PII>::const_iterator w=G[v].begin();w!=G[v].end();++w)
			if(C[v][w->st] > F[v][w->st] && w->nd + Dist[v]<Dist[w->st])
			{
				Dist[w->st] = w->nd + Dist[v];
				TT[w->st] = v;
				if(!u[w->st])
					u[w->st] = 1 , Q.push(w->st);
			}
		u[v] = 0;
	}
	if(Dist[D]!=INF)
	{
		drum = 1;
		for(int i=D;i!=S;i=TT[i])
			fmin = min(fmin,C[TT[i]][i] - F[TT[i]][i]);
		for(int i=D;i!=S;i=TT[i])
		{
			F[TT[i]][i]+=fmin;
			F[i][TT[i]]-=fmin;
		}
		return Dist[D]*fmin;
	}
	return 0;
}

ll solve()
{
	ll ans = 0 ;
	do	
	{	drum = 0;
		ans+=bellmanford();
	}	while(drum);
	return ans;
}

int main()
{
	read_data();
	fout<<solve()<<'\n';
	return 0;
}