#include <algorithm>
#include <iostream>
#include <fstream>
#include <climits>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <map>
#include <set>

#include <iomanip>
#include <cassert>

#include <random>
#include <chrono>

// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

using ull = unsigned long long;
//using ll = long long;

//#define int __int128
//#define int ll
#define pii pair <int, int>
#define all(a) (a).begin(), (a).end()
#define fr first
#define sc second
#define pb push_back
#define lb lower_bound
#define ub upper_bound

#define vt vector
#define FOR(a, b) for(int i = (a); i <= (b); i++)
#define FORr(a, b) for(int i = (a); i >= (b); i--)
#define sz(x) (int)(x).size()

#define YES cout << "YES\n"
#define NO cout << "NO\n"

using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int rangerng(int l, int r){
    return uniform_int_distribution<>(l, r)(rng);
}

string filename = "fmcm";
ifstream fin(filename + ".in");
ofstream fout(filename + ".out");

////////////////////////////////////////////////////////////////////////////////////

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

int n, m, s, d;
vt <pii> adj[NMAX + 1];
int f[NMAX + 1][NMAX + 1];

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

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

    queue <int> Q;
    Q.push(s);
    aux[s] = 0;
    inQ[s] = 1;

    while(!Q.empty()){
        int node = Q.front();
        Q.pop();
        inQ[node] = 0;
        //cout << node << endl;

        for(pii vec : adj[node]){
            if(f[node][vec.fr] > 0 && aux[node] + vec.sc < aux[vec.fr]){ // check flow here, so to not use back-edges!!!
                aux[vec.fr] = aux[node] + vec.sc;
                if(!inQ[vec.fr]){
                    inQ[vec.fr] = 1;
                    Q.push(vec.fr);
                }
            }
        }
    }
}

int real[NMAX + 1];
int dist[NMAX + 1];
int par[NMAX + 1];

bool DJK(){
    for(int i = 1; i <= n; i++){
        real[i] = dist[i] = INF;
        par[i] = 0;
    }

    priority_queue <pii, vector <pii>, greater <pii>> pq;
    dist[s] = real[s] = 0;
    pq.push({dist[s], s});

    while(!pq.empty()){
        int node = pq.top().sc;
        int val = pq.top().fr;
        pq.pop();

        if(val == dist[node]){
            for(pii vec : adj[node]){
                if(f[node][vec.fr] > 0 && dist[node] + vec.sc + aux[node] - aux[vec.fr] < dist[vec.fr]){
                    dist[vec.fr] = dist[node] + vec.sc + aux[node] - aux[vec.fr];
                    real[vec.fr] = real[node] + vec.sc;
                    par[vec.fr] = node;
                    pq.push({dist[vec.fr], vec.fr});
                }
            }
        }
    }

    return dist[d] != INF;
}

void solve(){
    fin >> n >> m >> s >> d;

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

    BF();

    int cost = 0;
    while(DJK()){
        int node = d, mini = INF;
        while(node != s){
            mini = min(mini, f[par[node]][node]);
            node = par[node];
        }

        cost += mini * real[d];

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

        for(int i = 1; i <= n; i++){
            aux[i] = real[i];
        }
    }

    fout << cost << '\n';
}   


signed main(){

    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int T;
    //fin >> T;

    T = 1;

    while(T--){
        solve();
    }

    return 0;
}

/*
*/