# include <fstream>
# include <vector>
# include <queue>
# include <set>
# include <cstring>
# define DIM 355
# define INF 1000000000
# define f first
# define s second
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
vector<pair<int,int> > Lista[DIM];
queue<int> q;
multiset<pair<int,int> > myset;
multiset<pair<int,int> >::iterator it;
int c[DIM][DIM],f[DIM][DIM],ct[DIM][DIM];
int Marcat[DIM],d[DIM],val[DIM],t[DIM],aux[DIM];
int n,m,nc,nv,i,j,sursa,destinatie,cost,flux,x,y,dif,sol;
void bellmanford(){
    for(int i=1;i<=n;i++)
        val[i]=INF;
    val[sursa]=0;
    q.push(sursa);
    while(!q.empty()){
        nc=q.front();
        q.pop();
        Marcat[nc]=0;
        for(int i=0;i<Lista[nc].size();i++){
            nv=Lista[nc][i].f;
            cost=Lista[nc][i].s;
            if(c[nc][nv]!=0&&val[nv]>val[nc]+cost){
                val[nv]=val[nc]+cost;
                if(Marcat[nv]==0){
                    Marcat[nv]=1;
                    q.push(nv);
                }
            }
        }
    }
}
bool fmcm(){
    for(int i=1;i<=n;i++)
        if(i!=sursa){
            d[i]=INF;
            aux[i]=INF;
        }
    myset.insert(make_pair(0,sursa));
    while(!myset.empty()){
        it=myset.begin();
        nc=it->s;
        int j=it->f;
        myset.erase(it);
        if(j!=d[nc])
            continue;
        for(int i=0;i<Lista[nc].size();i++){
            nv=Lista[nc][i].f;
            cost=Lista[nc][i].s;
            if(d[nv]>d[nc]+cost+val[nc]-val[nv]&&f[nc][nv]<c[nc][nv]){
                d[nv]=d[nc]+cost+val[nc]-val[nv];
                aux[nv]=aux[nc]+cost;
                myset.insert(make_pair(d[nv],nv));
                t[nv]=nc;
            }
        }
    }
    memcpy(val,aux,sizeof(aux));
    if(d[destinatie]==INF)
        return 0;
    return 1;
}
int main () {
    fin>>n>>m>>sursa>>destinatie;
    for(i=1;i<=m;i++){
        fin>>x>>y>>flux>>cost;
        Lista[x].push_back(make_pair(y,cost));
        Lista[y].push_back(make_pair(x,-cost));
        ct[x][y]=cost;
        ct[y][x]=-cost;
        c[x][y]=flux;
    }
    bellmanford();
    while(fmcm()){
        nv=destinatie;
        dif=INF;
        for(x=nv;t[x]!=0;x=t[x])
            dif=min(dif,c[t[x]][x]-f[t[x]][x]);
        for(x=nv;t[x]!=0;x=t[x]){
            f[t[x]][x]+=dif;
            f[x][t[x]]-=dif;
        }
        sol+=val[destinatie]*dif;
    }
    fout<<sol<<"\n";
    return 0;
}