#include<bits/stdc++.h>
#define pb push_back
#define ft first
#define maxn 355
#define sd second
#define inf 0x3f3f3f3f
using namespace std;
vector<int>v[maxn];
vector<int>::iterator dest;
pair<int,int> c[maxn][maxn];
int cost[maxn],heap[maxn],poz[maxn],tt[maxn],n,m,d,s,flux,Cost,k;
 
void upheap(int x){
    while(x!=1 && cost[heap[x]]<cost[heap[x/2]]){
        swap(heap[x],heap[x/2]);
        swap(poz[heap[x]],poz[heap[x/2]]);
        x/=2;
    }
}

void downheap(int x){
    int son=1;
    while(son){
        son=0;
        if(2*x<=k && cost[heap[x]]>cost[heap[2*x]])
            son=2*x;
        if(2*x+1<=k && cost[heap[x]]>cost[heap[2*x+1]] && cost[heap[2*x]]>cost[heap[2*x+1]])
            son=2*x+1;
        if(son){
            swap(poz[heap[x]],poz[heap[son]]);
            swap(heap[x],heap[son]);
        }
        x=son;
    }
}

void solve(){
	while(cost[d]!=inf){
		memset(cost, inf, sizeof(cost));
        cost[s]=0;
        heap[1]=s;
        k=poz[s]=1;
		while(k){
			int nod=heap[1];
            poz[nod]=0;
            swap(heap[1],heap[k]);
            poz[heap[1]]=1;
            k--; downheap(1);
			if(nod==d)
				continue;
			for(dest=v[nod].begin(); dest!=v[nod].end(); dest++){
				if(cost[nod]+c[nod][*dest].sd>=cost[*dest] || c[nod][*dest].ft==0)
					continue;
				cost[*dest]=cost[nod]+c[nod][*dest].sd;
				tt[*dest]=nod;
				if(poz[*dest]==0){
                    poz[*dest]=++k;
                    heap[k]=*dest;
                    upheap(k);
                }else upheap(poz[*dest]);
			}
		}
		if(cost[d]!=inf){
				flux=inf;
				if(cost[tt[d]]==inf  || c[tt[d]][d].ft==0)
					continue;
				for(int wh=d; wh!=s; wh=tt[wh])
					flux=min(flux, c[tt[wh]][wh].ft);
				for(int wh=d; wh!=s; wh=tt[wh])
					c[tt[wh]][wh].ft-=flux,
					c[wh][tt[wh]].ft+=flux;
				Cost+=flux*cost[d];
			}
	}
	cout<<Cost;
}
 
 
int main(){
	freopen("fmcm.in","r",stdin);
	freopen("fmcm.out", "w", stdout);
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin>>n>>m>>s>>d;
	int x,y,z,w;
	while(m--){
		cin>>x>>y>>w>>z;
		v[x].pb(y); v[y].pb(x);
		c[x][y].ft=w; c[x][y].sd=z; c[y][x].sd=-z;
	}
	solve();
	return 0;
}