#include <iostream>
#include <fstream>
#include <deque>
#include <vector>
#include <bitset>
#define dim 300
#define inf 1000000000
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
deque <int> q;
vector <int> L[dim];
bitset <dim> fr;
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]={inf};
bool bf()
{
    int nod,vecin;
    fr.reset();
    gasit=0;
    q.clear();
    q.push_back(s);
    fr[s]=1;
    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])
            {
                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;
    }
    D[s]=0;
    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];
    for(i=0;i<=n;i++)
        D[i]=inf;
    D[s]=0;
    }
    fout<<flux<<"\n";

}