// 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;
 
bool inQ[N + 1];
 
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();
 
		inQ[nod] = false;
 
		for(auto vec : adj[nod])
			if(aux[nod] + cost[nod][vec] < aux[vec] && f[nod][vec] > 0){
				aux[vec] = aux[nod] + cost[nod][vec];
				if(!inQ[vec])
					Q.push(vec), inQ[vec] = true;
			}
	}
}
 
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;
}