// retelistica extrem de nesimtita
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <climits>

using namespace std;

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

struct pii{
	int first, second;
	bool operator < (const pii &other) const
    {
        return second > other.second;
    }
};

const int N = 350, inf = INT_MAX;
int dist[N + 1], cdist[N + 1], from[N + 1], aux[N + 1];
int f[N + 1][N + 1], cost[N + 1][N + 1];
int n, m, S, D, maxFlow = 0, minCost = 0;

vector <int> adj[N + 1];

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

	queue <int> Q;
	Q.push(S), aux[S] = 0;

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

		for(auto vec : adj[nod])
			if(aux[nod] + cost[nod][vec] < aux[vec] && f[nod][vec] > 0)
				aux[vec] = aux[nod] + cost[nod][vec], Q.push(vec);
	}
}

priority_queue <pii> pq;
bool DJK(){
	for(int i = 1; i <= n; i++)
		dist[i] = cdist[i] = inf;

	pq.push({0, S});
	dist[S] = cdist[S] = 0;

	while(!pq.empty()){
		int nod = pq.top().second, val = pq.top().first;
		pq.pop();

		if(val == dist[nod])
			for(auto vec : adj[nod])
				if(f[nod][vec] > 0 && dist[nod] + cost[nod][vec] + aux[nod] - aux[vec] < dist[vec]){
					dist[vec] = dist[nod] + cost[nod][vec] + aux[nod] - aux[vec];
					cdist[vec] = cdist[nod] + cost[nod][vec];
					pq.push({dist[vec], vec}), from[vec] = nod;
				}
	}

	return(dist[D] != inf);
}

signed main(){

	fin >> n >> m >> S >> D;

	for(int i = 1; i <= m; i++){
		int a, b, cap, z;
		fin >> a >> b >> cap >> z;
		adj[a].push_back(b);
		adj[b].push_back(a);
		f[a][b] = cap, cost[a][b] = z, cost[b][a] -= z;
	}

	BF();

	while(DJK()){
		int nod = D, flow = inf;

		while(nod != S)
			flow = min(flow, f[from[nod]][nod]), nod = from[nod];

		nod = D, maxFlow += flow;

		while(nod != S)
			f[from[nod]][nod] -= flow, f[nod][from[nod]] += flow, nod = from[nod];
		
		minCost += flow * cdist[D];

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

	fout << minCost << '\n';

	return 0;
}