#include <bits/stdc++.h>
using namespace std;
#define maxb 8 ///buckets of bytes
#define bucket 0xFF //255,a byte aka bits 0-7(8 bits)
#define total_bytes (sizeof(vec[1]))
#define get_byte(x) ((x>>(byte*8))&bucket)
#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 400
const int inf=0x3f3f3f3f;

int N,M,S,D,cst[maxn][maxn],C[maxn][maxn],TT[maxn],inq[maxn];
int Cmin;
VI g[maxn];
priority_queue<PII,VPII,greater<PII>> heap;

bool fmcm()
{
	int d[N+5],nod,mini=inf;
	memset(d,inf,sizeof(d));
	d[S]=0;
	heap.push(mkp(d[S],S));
	for(;!heap.empty();)
	{
		nod=heap.top().nd;
		heap.pop();
		inq[nod]=0;
		for(auto it:g[nod])
			if(C[nod][it]){
				int newc=d[nod]+cst[nod][it];
				if(d[it]>newc){
					d[it]=newc;
					TT[it]=nod;
					if(!inq[it])heap.push(mkp(newc,it)),inq[it]=1;
				}
			}
	}
	for(int aux=D;aux!=S;aux=TT[aux])
		mini=min(mini,C[TT[aux]][aux]);
	Cmin+=(mini*d[D]);
	for(int aux=D;aux!=S;aux=TT[aux])
		C[TT[aux]][aux]-=mini,C[aux][TT[aux]]+=mini;
	return((d[D]==inf)?0:1);
}

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);
		cst[x][y]=z,cst[y][x]=-z;
		C[x][y]=c;
	}
	for(;fmcm(););
	cout<<Cmin;
}