#include <fstream>
#include <vector>
using namespace std;
#define NMAX 360
#define oo 2000000000
int n,S,D;
vector <int> A[NMAX];
int nv[NMAX],Dist[NMAX], viz[NMAX],Q[NMAX];
int C[NMAX][NMAX],F[NMAX][NMAX], Cost[NMAX][NMAX];
bool inq[NMAX],Drum;

void citire()
{
	ifstream fin("fmcm.in");
	int m;
	fin>>n>>m>>S>>D;
	for (int i=0;i<m;++i)
	{ int x,y,cap,z;
		fin>>x>>y>>cap>>z;
		A[x].push_back(y);
		A[y].push_back(x);
		C[x][y]=cap;
		Cost[x][y]=z; Cost[y][x]=-z;
	}
	for (int i=1;i<=n;++i) nv[i]=A[i].size();
	fin.close();
}

int BellmanFord()
{ int i,lq,j;
	for (i=1;i<=n;++i) 
	 {Dist[i]=oo; viz[i]=-1;}
	Dist[S]=0; 
	memset(inq,0,sizeof(inq));
	lq=1; Q[1]=S; inq[S]=true;
	for (i=1;i<=lq;++i)
	{
		int x=Q[i]; 
		for (j=0;j<nv[x];++j)
		 if (C[x][A[x][j]]>F[x][A[x][j]] && Dist[A[x][j]]>Dist[x]+Cost[x][A[x][j]])
			{ 
				Dist[A[x][j]]=Dist[x]+Cost[x][A[x][j]];
				viz[A[x][j]]=x;
				if (!inq[A[x][j]])
					{
						Q[++lq]=A[x][j];
						inq[A[x][j]]=true;
					}
			}		
		inq[x]=0;
	}
	
	if (Dist[D]!=oo)
	{
		Drum=true;
		int fluxmin=oo;
		for (i=D; i!=S;i=viz[i])
		 fluxmin=min(fluxmin,C[viz[i]][i]-F[viz[i]][i]);
		for (i=D; i!=S; i=viz[i])
		{
		 F[viz[i]][i]+=fluxmin;
		 F[i][viz[i]]-=fluxmin;
		}
		
		return fluxmin*Dist[D];
	}	
	else return 0;
}

long long flux()
{
	long long fmcm=0;
	do
	{
		Drum=0;
		fmcm+=BellmanFord();
	}
	while (Drum);
	return fmcm;
}

void afisare(long long f)
{
	ofstream fout("fmcm.out");
	fout<<f;
	fout.close();
}

int main()
{
	citire();
	afisare(flux());
	return 0;
}