#include <fstream>
#include <cstring>
using namespace std;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

typedef struct nod
{
    int inf;
    nod *urm;
} NOD;

int G[360][360],C[360][360];
int n,m,S,D;
int t[360],v[360],d[360],inq[360];
int cost,maxFlow;

void citire()
{
    f>>n>>m>>S>>D;
    int x,y,c,z;
    while(m--)
    {
        f>>x>>y>>c>>z;
        G[x][y]=c;
        C[x][y]=z;
        C[y][x]=-z;
    }
    f.close();
}

void bellmanFord()
{
    int x=S;
    NOD *queue=new NOD;
    queue->inf=x;queue->urm=NULL;
    memset(d,0,sizeof(d));
    memset(t,0,sizeof(t));
    memset(inq,0,sizeof(inq));
    for(NOD *p=queue,*aux;p;aux=p,p=p->urm,delete aux)
    {
        int i=p->inf;
        for(int j=1;j<=n;j++)
        {
            if(G[i][j]>0&&(d[i]+C[i][j]<d[j]||!d[j])&&j!=S)
            {
                d[j]=d[i]+C[i][j];
                t[j]=i;
                if(!inq[j])
                {
                    NOD *q=new NOD;
                    q->inf=j;q->urm=NULL;queue->urm=q;queue=q;
                    inq[j]=1;
                }
            }
        }
        inq[i]=0;
    }
}

int main()
{
    citire();
    bellmanFord();
    while(d[D])
    {
        int minn=2000000000;
        for(int i=D;t[i];i=t[i])
            if(G[t[i]][i]<minn)
                minn=G[t[i]][i];
        cost+=minn*d[D];
        for(int i=D;t[i];i=t[i])
            if(G[t[i]][i]>0)
            {
                G[t[i]][i]-=minn;
                G[i][t[i]]+=minn;
            }
        bellmanFord();
    }
    g<<cost<<'\n';
    g.close();
    return 0;
}