#include <bits/stdc++.h>

using namespace std;

int n, m, s, d;

vector<vector<int> >graph, capacity, flow, cost;
vector<int> parent;

vector<int> dist;

struct cmp{
    bool operator()(int a, int b){
        return dist.at(a) > dist.at(b);
    }
};

priority_queue<int, vector<int>, cmp> pQueue;

bool dijkstra(){

    dist.clear();
    dist.resize(n+1, INT_MAX);
    parent.clear();
    parent.resize(n+1);

    vector<bool> inQueue = vector<bool>(n+1, false);
    dist.at(s) = 0;
    pQueue.push(s);

    while(!pQueue.empty()){
        int node = pQueue.top();
        pQueue.pop();
        inQueue.at(node) = false;

        for(auto& neighbour:graph.at(node)){
            if(capacity.at(node).at(neighbour)==flow.at(node).at(neighbour)) continue;

            if(dist.at(node)+cost.at(node).at(neighbour) < dist.at(neighbour)){
                dist.at(neighbour) = dist.at(node)+cost.at(node).at(neighbour);

                parent.at(neighbour) = node;


                if(!inQueue.at(neighbour)){
                    inQueue.at(neighbour) = true;
                    pQueue.push(neighbour);
                }
            }
        }

    }

    if(dist.at(d)!=INT_MAX) return true;


    return false;
}

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

    fin>>n>>m>>s>>d;

    int x, y, z, c;

    graph.resize(n+1, vector<int>());
    capacity.resize(n+1, vector<int>(n+1));
    flow.resize(n+1, vector<int>(n+1));
    cost.resize(n+1, vector<int>(n+1));

    for(int i=1; i<=m; i++){
        fin>>x>>y>>z>>c;
        graph.at(x).push_back(y);
        graph.at(y).push_back(x);
        cost.at(x).at(y) = c;
        cost.at(y).at(x) = - c;
        capacity.at(x).at(y) = z;
    }

    int cmin = 0, cflow;

    while(dijkstra()){
        cflow = INT_MAX;

        for(int i=d; i!=s; i = parent.at(i))
            cflow = min(cflow, capacity.at(parent.at(i)).at(i) - flow.at(parent.at(i)).at(i));

        for(int i=d; i!=s; i = parent.at(i)){
            flow.at(parent.at(i)).at(i) += cflow;
            flow.at(i).at(parent.at(i)) -= cflow;

            cmin += cost.at(parent.at(i)).at(i)*cflow;
        }

    }

    fout<<cmin;

}