#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
#include <string.h>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <time.h>
#include <stdlib.h>
#include <set>
#include <map>
#include <string>
#include <queue>
#include <unordered_map>

using namespace std;

const char infile[] = "fmcm.in";
const char outfile[] = "fmcm.out";

ifstream fin(infile);
ofstream fout(outfile);

const int MAXN = 100005;
const int oo = 0x3f3f3f3f;

typedef vector<int> :: iterator It;

const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }

class Graph {
private:
    vector <vector <pair<int, int> > > g;
    unordered_map<int, unordered_map<int, int> > capacity;
    int N;
    queue <int> q;
    vector <bool> inq;
    vector <int> dist, father;
public:
    Graph() {
    }
    Graph(int N) {
        this->N = N;
        g.resize(N);
        inq.resize(N);
        dist.resize(N);
        father.resize(N);
    }
    inline void addDirectedEdge(int x, int y, int cap, int cost) {
        g[x].push_back(make_pair(y, cost));
        capacity[x][y] = cap;
    }
    inline int getMinCostMaxFlow(int source, int sink) {
        int mincostmaxflow = 0;
        while(bellmanford(source, sink)) {
            int bottleneck = oo;
            for(int i = sink ; i != source ; i = father[i])
                bottleneck = min(bottleneck, capacity[father[i]][i]);
            if(!bottleneck)
                continue;
            for(int i = sink ; i != source ; i = father[i]) {
                capacity[father[i]][i] -= bottleneck;
                capacity[i][father[i]] += bottleneck;
            }
            mincostmaxflow += bottleneck * dist[sink];
        }
        return mincostmaxflow;
    }
    inline bool bellmanford(int source, int sink) {
        fill(dist.begin(), dist.end(), oo);
        q.push(source);
        inq[source] = true;
        dist[source] = 0;
        while(!q.empty()) {
            int node = q.front();
            q.pop();
            inq[node] = false;
            for(auto it:g[node])
                if(capacity[node][it.first] > 0 && dist[it.first] > dist[node] + it.second) {
                    dist[it.first] = dist[node] + it.second;
                    father[it.first] = node;
                    if(inq[it.first])
                        continue;
                    q.push(it.first);
                    inq[it.first] = true;
                }
        }
        return dist[sink] != oo;
    }
};

int N, M, S, D;

int main() {
    fin >> N >> M >> S >> D;
    Graph G(N);
    for(int i = 1 ; i <= M ; ++ i) {
        int x, y, cap, cost;
        fin >> x >> y >> cap >> cost;
        G.addDirectedEdge(x-1, y-1, cap, cost);
        G.addDirectedEdge(y-1, x-1,   0,-cost);
    }
    fout << G.getMinCostMaxFlow(S - 1, D - 1) << '\n';
    fin.close();
    fout.close();
    return 0;
}