/* 
 * File:   main.cpp
 * Author: VirtualDemon
 *
 * Created on April 14, 2010, 3:51 PM
 */
#include <queue>
#include <cstdlib>
#include <fstream>
#define Nmax 400
#define SIZE 8219
#define oo 0x3f3f3f3f

/*
 *
 */
using namespace std;
ifstream in;
typedef pair< int, int > pr;
int N, s, sk, ifile;
char file[SIZE];
int C[Nmax][Nmax];
int d[Nmax], f[Nmax];
vector< pr > G[Nmax];
vector< pr >::const_iterator it, iend;
class cmp
{
public:
    inline bool operator() ( const int& x, const int& y ) const
    {
        return d[x] > d[y];
    }
};
priority_queue< int, vector< int >, cmp > PQ;
inline void read( int& x )
{
    int semn=1;
    x=0;
    while( file[ifile] < '0'  || file[ifile] > '9' )
    {
        if( '-' == file[ifile] )
            semn=-1;
        if( ++ifile == SIZE )
        {
            in.read( file, SIZE );
            ifile=0;
        }
    }
    while( file[ifile] >= '0' && file[ifile] <= '9' )
    {
        x=x*10+file[ifile]-'0';
        if( ++ifile == SIZE )
        {
            in.read( file, SIZE );
            ifile=0;
        }
    }
    x*=semn;
}
inline int find_path( void )
{
    int x, c;
    vector< bool > inH( N );
    for( x=0; x < N; d[x]=oo, ++x );
    d[s]=0;
    f[s]=f[sk]=-1;
    for( PQ.push(s); !PQ.empty();  )
    {
        x=PQ.top(); PQ.pop();
        inH[x]=false;
        for( it=G[x].begin(), iend=G[x].end(); it < iend; ++it )
            if( C[x][it->first] > 0 && d[it->first] > d[x]+it->second )
            {
                f[it->first]=x;
                d[it->first]=d[x]+it->second;
                if( !inH[it->first] )
                {
                    PQ.push(it->first);
                    inH[it->first]=true;
                }
            }
    }
    if( -1 == f[sk] )
        return 0;
    for( x=sk, c=oo; -1 != f[x]; x=f[x] )
        c=min( c, C[f[x]][x] );
    for( x=sk; -1 != f[x]; x=f[x] )
    {
        C[x][f[x]]+=c;
        C[f[x]][x]-=c;
    }
    return d[sk]*c;
}
inline int MaxFlowMinCost( void )
{
    int s, p;
    for( s=0, p=find_path(); p; s+=p, p=find_path() );
    return s;
}
int main( void )
{
    int M, x, y, c;
    in.open( "fmcm.in" );
    read(N); read(M); read(s); read(sk);
    --s, --sk;
    for( ; M; --M )
    {
        read(x), read(y), read( C[x-1][y-1] ), read(c);
        --x, --y;
        G[x].push_back( pr( y, c ) );
        G[y].push_back( pr( x, -c ) );
    }
    ofstream out( "fmcm.out" );
    out<<MaxFlowMinCost()<<'\n';
    return EXIT_SUCCESS;
}