#include <algorithm>
#include <bitset>
#include <cstring>
#include <fstream>
#include <queue>
#include <vector>
using namespace std;
const int Dim = 351;
const int Inf = 0x3f3f3f3f;
short int N, M, S, D;
short int t[Dim], cp[Dim][Dim], fl[Dim][Dim];
int ans, c[Dim];
bitset <Dim> f;
vector < pair <short int, short int> > v[Dim];
struct cmp
{
    bool operator()( short int x, short int y ) 
	{
        return c[x] > c[y];
    }
};
priority_queue < short int, vector <short int>, cmp > h;
int BellmanFord()
{
    short int nod;
    int fm;
    vector < pair <short int, short int> > :: iterator it;
    memset( c, Inf, sizeof( c ) );
    memset( t, 0, sizeof( t ) );
    c[S] = 0;
    h.push( S );
    f[S] = true;
    while( !h.empty() ) 
	{
        nod = h.top();
        h.pop();
        f[nod] = false;
        for( it = v[nod].begin(); it != v[nod].end(); ++it )
            if( cp[nod][it->first] - fl[nod][it->first] > 0 && c[nod] + it->second < c[it->first] )
			{
                c[it->first] = c[nod] + it->second;
                t[it->first] = nod;
                if( f[it->first] == false ) 
				{
                    h.push( it->first );
                    f[it->first] = true;
                }
            }
    }
    if( c[D] != Inf ) 
	{
        fm = Inf;
        for( nod = D; t[nod]; nod = t[nod] )
            fm = min( fm, cp[t[nod]][nod] - fl[t[nod]][nod] );
        for( nod = D; t[nod]; nod = t[nod] ) 
		{
            fl[t[nod]][nod] += fm;
            fl[nod][t[nod]] -= fm;
        }
    }
    else fm = 0;
    return fm * c[D];
}
int main()
{
    ifstream fin( "fmcm.in");
    ofstream fout( "fmcm.out" );
    int x, y, z, t;
    int r;
    fin >> N >> M >> S >> D;
    while( M-- )
	{
        fin >> x >> y >> z >> t;
        v[x].push_back( make_pair( y, t ) );
        v[y].push_back( make_pair( x, -t ) );
        cp[x][y] = z;
    }
	r=1;
	while (r)
	{
        r = BellmanFord();
        ans += r;
    }
    fout <<ans;
    return 0;
}