#include <queue>
#include <vector>
#include <fstream>
#include <cstdlib>
#define N_MAX 361
#define oo 1<<20
#define pr pair< int, int >
#define mkpr make_pair< int, int >

using namespace std;
int N, source, sink;
int C[N_MAX][N_MAX];
vector< pr > G[N_MAX];
vector< int > d;
vector< pr >::const_iterator it, iend;
class cmp
{
public :
	inline bool operator() ( const int& x, const int& y ) { return d[x] > d[y]; }
};
inline int _min( int x, int y ) { return ( x <= y ? x : y ); } 
inline int findPath()
{
	int x;
	vector< bool > was( N+1 );
	vector< int > f( N+1, -1 );
	priority_queue< int, vector<int>, cmp > pQ;
	f[source]=-2;
	d.assign( N+1, oo );
	d[source]=0;
	for( pQ.push(source); !pQ.empty(); )
	{
		x=pQ.top(); pQ.pop();
		was[x]=false;
		for( it=G[x].begin(), iend=G[x].end(); it < iend; ++it )
		{
			if( source == it->first )
				continue;
			if( d[it->first] > d[x]+it->second && C[x][it->first] > 0 )
			{
				f[it->first]=x;
				d[it->first]=d[x]+it->second;
				if( false == was[it->first] )
				{
					pQ.push(it->first);
					was[it->first]=true;
				}
			}
		}
	}
	if( -1 == f[sink] || oo == d[sink] )
		return -oo;
	int min=oo;
	for( x=sink; -2 != f[x]; x=f[x] )
		min=_min( min, C[f[x]][x] );
	for( x=sink; -2 != f[x]; x=f[x] )
	{
		C[f[x]][x]-=min;
		C[x][f[x]]+=min;
	}
	return d[sink]*min;
}
int MaxFlow()
{
	int s, pathC;
	for( s=0, pathC=findPath(); -oo != pathC; s+=pathC, pathC=findPath() );
	return s;
}
int main( void )
{
	int M, x, y, cost;
	ifstream in( "fmcm.in" );
	for( in>>N>>M>>source>>sink; M; --M )
	{
		in>>x>>y;
		in>>C[x][y]>>cost;
		G[x].push_back( mkpr( y, cost ) );
		G[y].push_back( mkpr( x, -cost ) );
	}
	d.resize( N+1 );
	ofstream out( "fmcm.out" );
	out<<MaxFlow()<<'\n';
	return EXIT_SUCCESS;
}