#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
#include <deque>
#include <climits>
#define DIM 400
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
deque<int> q;
bitset<DIM> f;
int i,n,m,z,c,x,y,flux[DIM][DIM],Z[DIM][DIM],r[DIM][DIM],s,d,rasp,D[DIM],T[DIM],minim,ok,nod;
vector<int> L[DIM];
int ford(){
    f.reset();
    for(int i=1;i<=n;i++)
        D[i]=INT_MAX;

    q.push_back(s);
    D[s]=ok=0;
    f[s]=1;
    while(!q.empty()){
        nod=q.front();
        q.pop_front();
        f[nod]=0;
        for(int i=0;i<L[nod].size();i++){
            int vec=L[nod][i];
            if((D[vec]>D[nod]+Z[nod][vec])&&(r[nod][vec]>flux[nod][vec])){
                D[vec]=D[nod]+Z[nod][vec];
                T[vec]=nod;
                if(f[vec]==0){
                    q.push_back(vec);
                    f[vec]=1;
                    if(vec==d)
                        ok=1;
                }

            }

        }
    }
    return ok;
}
int main(){
    fin>>n>>m>>s>>d;
    for(i=1;i<=m;i++){
        fin>>x>>y>>c>>z;
        L[x].push_back(y);
        L[y].push_back(x);
        r[x][y]=c;
        Z[x][y]=z;
        Z[y][x]=-z;
    }

    while(ford()){

        nod=d;
        minim=INT_MAX;
        while(nod!=s){
            minim=min(minim,r[T[nod]][nod]-flux[T[nod]][nod]);
            nod=T[nod];
        }
        nod=d;
        while(nod!=s){
            flux[T[nod]][nod]+=minim;
            flux[nod][T[nod]]-=minim;
            nod=T[nod];
        }
        rasp+=minim*D[d];
    }
    fout<<rasp;
    return 0;
}