#include <stdio.h>
#include <string.h>
#include <vector>
#include <queue>
#define MAX 355
#define INF 1<<30
#define mp make_pair
#define pair pair<int,int>
#define min(a, b) (a < b ? a : b)
using namespace std;

int n, m, i, x, y, c, z, G[MAX][MAX], C[MAX][MAX], cost[MAX][MAX];
int source, dest, minim, flow, parent[MAX];
int DB[MAX], DD[MAX], DR[MAX];
vector<int> l[MAX];
queue<int> q;
bool viz[MAX];

priority_queue< pair, vector<pair>, greater<pair> > pq;

void BellmanFord(int s);
bool Dijkstra(int s);

int main(){
	freopen("fmcm.in", "r", stdin);
	freopen("fmcm.out", "w", stdout);
	scanf("%d%d%d%d", &n, &m, &source, &dest);
	for(i = 0; i < m; i++){
		scanf("%d%d%d%d", &x, &y, &c, &z);
		C[x][y] = c;
		cost[x][y] = z;
		l[x].push_back(y);
		cost[y][x] = -z;
		l[y].push_back(x);
	}

	BellmanFord(source);

	while(Dijkstra(source)){
		minim = INF;
		int v = dest;
		while(v != parent[v]){
			int u = parent[v];
			minim = min(minim, C[u][v] - G[u][v]);
			v = u;
		}
		v = dest;
		while(v != parent[v]){
			int u = parent[v];
			G[u][v] += minim;
			G[v][u] -= minim;
			v = u;
		}
		flow += minim * DB[dest];
	}

	printf("%d", flow);
	return 0;
}

void BellmanFord(int s){
	memset(DB, INF, n + 1);
	DB[s] = 0;
	viz[s] = true;
	
	for(q.push(s); !q.empty(); q.pop()){
		i = q.front();
		viz[i] = false;
		for(vector<int>::iterator it = l[i].begin(); it < l[i].end(); it++){
			if(DB[*it] > DB[i] + cost[i][*it] && G[i][*it] < C[i][*it]){
				DB[*it] = DB[i] + cost[i][*it];
				if(!viz[*it]){
					viz[*it] = true;
					q.push(*it);
				}
			}
		}
	}
}

bool Dijkstra(int s){
	for(i = 1; i <= n; i++)
        DD[i] = INF;
	DD[s] = 0;
	pq.push(mp(0, s));
	parent[s] = s;

	while(!pq.empty()){
		int aux = pq.top().second;
		int costaux = pq.top().first;
		pq.pop();

		if(costaux > DD[aux])
			continue;

		for(vector<int>::iterator it = l[aux].begin(); it < l[aux].end(); it++)
			if(G[aux][*it] < C[aux][*it])
				if(DD[aux] + cost[aux][*it] + DB[aux] - DB[*it] < DD[*it]){
					DD[*it] = DD[aux] + cost[aux][*it] + DB[aux] - DB[*it];
					DR[*it] = DR[aux] + cost[aux][*it];
					parent[*it] = aux;
					pq.push(mp(DD[*it], *it));
				}
	}

	for(i = 1; i <= n; i++)
		DB[i] = DR[i];
	return DD[dest] != INF;
}