#include <algorithm>
#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <queue>

#include <iomanip>

#define pii pair <int, int>

using namespace std;

string filename = "fmcm";

#ifdef LOCAL
    ifstream fin("input.in");
    ofstream fout("output.out");
#else
    ifstream fin(filename + ".in");
    ofstream fout(filename + ".out");
#endif

const int NMAX = 350;
const int INF = 1e9;

int n, m;
vector <pii> adj[NMAX + 1];
int flow[NMAX + 1][NMAX + 1];

int aux[NMAX + 1];
bool inQ[NMAX + 1];

void BF(int source){
    for(int i = 1; i <= n; i++){
        aux[i] = INF, inQ[i] = false;
    }

    queue <int> Q;
    Q.push(source);
    inQ[source] = true;
    aux[source] = 0;

    while(!Q.empty()){
        int node = Q.front();

        Q.pop();
        inQ[node] = false;

        for(pii vec : adj[node]){
            if(aux[node] + vec.second < aux[vec.first] && flow[node][vec.first] > 0){
                aux[vec.first] = aux[node] + vec.second;
                if(!inQ[vec.first]){
                    Q.push(vec.first);
                }   
            }
        }
    }
}   

bool viz[NMAX + 1];
int parent[NMAX + 1];

int fakedist[NMAX + 1];
int realdist[NMAX + 1];

priority_queue <pii, vector <pii>, greater <pii>> pq;
bool DJK(int source, int destination){
    for(int i = 1; i <= n; i++){
        viz[i] = false;
        fakedist[i] = realdist[i] = INF;
    }
    
    while(!pq.empty()){
        pq.pop();
    }

    fakedist[source] = realdist[source] = 0;
    pq.push({fakedist[source], source});

    while(!pq.empty()){
        int node = pq.top().second;
        pq.pop();

        if(!viz[node]){
            viz[node] = true;

            for(pii vec : adj[node]){
                if(flow[node][vec.first] > 0 && fakedist[node] + vec.second + aux[node] - aux[vec.first] < fakedist[vec.first]){
                    fakedist[vec.first] = fakedist[node] + vec.second + aux[node] - aux[vec.first];
                    realdist[vec.first] = realdist[node] + vec.second;
                    parent[vec.first] = node;
                    pq.push({fakedist[vec.first], vec.first});
                }
            }
        }
    }

    return (fakedist[destination] != INF);
}

signed main(){

    int s, d;
    fin >> n >> m >> s >> d;

    for(int i = 1; i <= m; i++){
        int a, b, c, d;
        fin >> a >> b >> c >> d;
        adj[a].push_back({b, +d});
        adj[b].push_back({a, -d});
        flow[a][b] = +c;
    }

    BF(s);

    int maxFlow = 0;
    int minCost = 0;

    while(DJK(s, d)){
        int mini = INF, node = d;
        while(node != s){
            mini = min(mini, flow[parent[node]][node]);
            node = parent[node];
        }

        if(mini == 0){
            continue;
        }

        node = d;
        while(node != s){
            flow[parent[node]][node] -= mini;
            flow[node][parent[node]] += mini;
            node = parent[node];
        }

        maxFlow += mini;
        minCost += mini * realdist[d];
            
        
    }

    fout << minCost << '\n';

    return 0;
}