#include <fstream>
#include <vector>
#include <bitset>
#include <queue>
#define DIM 355

using namespace std;

ifstream fin("fmcm.in");
ofstream fout("fmcm.out");

int N, M, S, D, minim, Cost;
bitset <DIM> inQueue;

vector <int> v[DIM];
int C[DIM][DIM];
int F[DIM][DIM];
int cost[DIM][DIM];
int Di[DIM];
int T[DIM];

queue <int> Q;

int BF(){

    inQueue.reset();

    inQueue[S]=1;
    for(int i=1;i<=N;i++)
        Di[i]=0x3f3f3f3f;
    Di[S]=0;
    Q.push(S);
    while(!Q.empty()){
        int node = Q.front();
        Q.pop();
        inQueue[node] = 0;
        for(std::vector <int>::iterator it=v[node].begin();it!=v[node].end();it++){
            int vec = *it;
            if(C[node][vec] > F[node][vec] && Di[vec] > Di[node] + cost[node][vec]){
                Di[vec] = Di[node] + cost[node][vec];
                T[vec] = node;
                if(!inQueue[vec]){
                    inQueue[vec] = 1;
                    Q.push(vec);
                }
            }
        }
    }
    if(Di[D] != 0x3f3f3f3f)
        return 1;
    return 0;
}

int main(){

    fin >> N >> M >> S >> D;
    for(int i=1;i<=M;i++){
        int x,y,z,w;
        fin >> x >> y >> z >> w;

        C[x][y] = z;
        cost[x][y] = w;
        cost[y][x] = -w;

        v[x].push_back(y);
        v[y].push_back(x);
    }

    while(BF()){
        minim = 0x3f3f3f3f;
        int U = D;
        while(U!=S){
            if(minim > C[T[U]][U] - F[T[U]][U])
                minim = C[T[U]][U] - F[T[U]][U];
            U = T[U];
        }
        U = D;
        while(U!=S){
            Cost += minim * cost[T[U]][U];
            F[T[U]][U] += minim;
            F[U][T[U]] -= minim;
            U = T[U];
        }
    }

    fout << Cost << "\n";

}