#include <iostream>
#include <fstream>
#include <cmath>
#include <vector>
#include <bitset>
#include <queue>
#include <deque>
#include <list>
#include <set>
#include <ctime>
#include <string>
#include <cstring>
#include <iomanip>
#include <algorithm>
using namespace std;
ifstream ff("fmcm.in");
ofstream gg("fmcm.out");
#define max 352 

vector<int> vv[max];
int n, m, s, d, cc[max][max], zz[max][max], qq[2][max], q0, q1, ww[max];
int dd[max], tt[max], rr[max][max], aa[max], bb[max];

bool bel(){
	int x0=0, x1=1, a, b, l;
	q0=q1=0;
	memset(ww, 0, sizeof(ww));
	for(int i=1;i<=n;i++) dd[i]=0xfffffff;
	qq[x0][q0++]=s;
	ww[s]=1;
	dd[s]=0;
	for(int k=1;k<=n;k++){
		while(q0>0){
			a=qq[x0][--q0];
			if(a==d) continue;
			l=vv[a].size();
			for(int i=0;i<l;i++){
				b=vv[a][i];
				if(dd[b]>dd[a]+zz[a][b] && rr[a][b]<cc[a][b]){
					dd[b]=dd[a]+zz[a][b];
					if(ww[b]!=k) qq[x1][q1++]=b;
					ww[b]=k;
					tt[b]=a;
				}
			}
		}
		x0^=1; x1^=1; swap(q0, q1);
	}
	return ww[d];
}

struct per{ int v, x; per(int v0=0, int x0=0){v=v0;x=x0;}
	bool operator()(const per &a, const per &b){ return a.v>b.v; }
};

priority_queue<per, vector<per>, per> hh;

bool dij(){
	per a;
	int x, y, c, v;
	for(int i=1;i<=n;i++) aa[i]=0xfffffff;
	aa[s]=0; bb[s]=0;
	hh.push(per(0,s));
	while(!hh.empty()){
		a=hh.top(); hh.pop();
		x=a.x;
		c=a.v;
		if(aa[x]!=c) continue;
		if(x==d) continue;
		for(int i=0;i<(int)vv[x].size();i++){
			y=vv[x][i];
			if(rr[x][y]<cc[x][y]){
				v=aa[x]+zz[x][y]+dd[x]-dd[y];
				if(v<aa[y]){
					aa[y]=v;
					tt[y]=x;
					bb[y]=bb[x]+zz[x][y];
					hh.push(per(aa[y], y));
				}
			}
		}
	}
	memcpy(dd, bb, sizeof(bb));
	return aa[d]!=0xfffffff;
}

void flu(){
	int r=0, c;
	bel();
	
	while(dij()) {
		c=0xfffffff;
		for(int x=d;x!=s;x=tt[x])c=min(c, cc[tt[x]][x]-rr[tt[x]][x]);
		if(c!=0){
			for(int x=d;x!=s;x=tt[x]){
				rr[tt[x]][x] += c;
				rr[x][tt[x]] -= c;
				r+=c*zz[tt[x]][x];
			}
		}
	}
	gg << r << "\n";
}

int main(){
	int a, b, c, z;
	ff >> n >> m >> s >> d;
	for(int i=0;i<m;i++){
		ff >> a >> b >> c >> z;
		vv[a].push_back(b);
		vv[b].push_back(a);
		cc[a][b]=c;
		zz[a][b]=z;
		zz[b][a]=-z;
	}
	flu();
}