#include <bits/stdc++.h>
using namespace std;
#define st first
#define nd second
#define pb push_back
#define mkp make_pair
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define FORS(i,a,b) for(int i=(a);i<(b);++i)
#define PII pair<int,int>
#define VI vector<int>
#define VPII vector<PII>
#define all(x) x.begin(),b.end()
#define SZ(x) ((int)(x).size())
#define ll long long
#define MOD 10000000 //998244353
#define maxn 355
const int INF=0x3f3f3f3f;

int N,M,S,D,cst[maxn][maxn],C[maxn][maxn],nod,mini,
TT[maxn],Cmin,d[maxn];
VI g[maxn];
priority_queue<PII,VPII,greater<PII>>que;

bool fmcm()
{
	FOR(i,1,N)d[i]=INF;
	d[S]=0;
	que.push(mkp(d[S],S));
	while(!que.empty())
	{
		nod=que.top().nd;
		que.pop();
		for(auto it:g[nod])
			if(C[nod][it]){
				int newc=d[nod]+cst[nod][it];
				if(newc<d[it]){
					d[it]=newc;
					TT[it]=nod;
					que.push(mkp(newc,it));
				}
			}
	}
	if(d[D]==INF)return 0;
	mini=INF;
	for(int u=D;u!=S;u=TT[u])
		mini=min(mini,C[TT[u]][u]);
	for(int u=D;u!=S;u=TT[u])
		C[TT[u]][u]-=mini,C[u][TT[u]]+=mini;
	Cmin+=(mini*d[D]);
	return 1;
}

int main()
{
	freopen("fmcm.in","r",stdin);
	freopen("fmcm.out","w",stdout);
	int x,y,c,z;
	cin>>N>>M>>S>>D;
	FOR(i,1,M){
		cin>>x>>y>>c>>z;
		g[x].pb(y);
		g[y].pb(x);
		C[x][y]=c;
		cst[x][y]=z,cst[y][x]=-z;
	}
	for(;fmcm(););
	cout<<Cmin;
}