#include <bits/stdc++.h>
#define dim 353
#define inf 100000000
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
deque <int> q;
vector <int> L[dim];
bool fr[dim];
int Z[dim][dim];
int flux,j,cp,cost,nod;
int C[dim][dim], F[dim][dim],i,p,u,minim,T[dim],n,x,y,s,d,m,gasit,D[dim];

bool bf()
{
   memset(fr,0,sizeof(fr));
    int nod,vecin,i;
    for(i=1; i<=n; i++)
        D[i]=inf;
    D[s]=0;
    gasit=0;
    q.clear();
    q.push_back(s);
    while(!q.empty())
    {
        nod=q.front();
        q.pop_front();
        fr[nod]=0;
        for(i=0; i<L[nod].size(); i++)
        {
            vecin=L[nod][i];
            if(C[nod][vecin]>F[nod][vecin] && D[vecin] > D[nod]+ Z[nod][vecin])
            {
                //   cout<<1;
                D[vecin] = D[nod]+Z[nod][vecin];
                T[vecin]=nod;
                if(!fr[vecin])
                {
                    q.push_back(vecin);
                    fr[vecin]=1;
                    if(vecin==d)
                        gasit=1;
                }

            }

        }
    }
    return gasit;

}


int main()
{
    fin>>n>>m>>s>>d;
    for(i=1; i<=m; i++)
    {
        fin>>x>>y>>cp>>cost;
        L[x].push_back(y);
        L[y].push_back(x);
        C[x][y]=cp;
        Z[x][y]=cost;
        Z[y][x]=-cost;
    }

    while (bf())
    {
        nod=d;
        minim=inf*2;
        while(nod!=s)
        {
            minim=min(minim,C[T[nod]][nod]-F[T[nod]][nod]);
            nod=T[nod];
        }
        nod=d;
        while(nod!=s)
        {
            F[T[nod]][nod] +=minim;
            F[nod][T[nod]] -=minim;
            nod=T[nod];
        }
        flux+=minim*D[d];

    }
    fout<<flux<<"\n";

}