#include <fstream>
#include <list>
#include <queue>
#include <bitset>
#define DIM 361
#define INF 2000000011
using namespace std;
ifstream f("fmcm.in");
ofstream g("fmcm.out");
int N,M,X,Y,minim;
int D[DIM],T[DIM];
int F[DIM][DIM],C[DIM][DIM],CT[DIM][DIM];
long long sol;

list<int> L[DIM];
queue<int> q;
bitset<DIM> viz;

int bellmanford(){
    list<int>::iterator it;
    register int i,nod;
    viz.reset();
    q.push(X);
    viz[X]=1;
    for(i=1;i<=N;i++) D[i]=INF,T[i]=-1;
    D[X]=0;

    while(!q.empty()){
        nod=q.front(),q.pop(),viz[nod]=0;
        for(it=L[nod].begin();it!=L[nod].end();it++){
            if(C[nod][*it]>F[nod][*it] && D[nod]+CT[nod][*it]<D[*it]){
                D[*it]=D[nod]+CT[nod][*it];
                T[*it]=nod;
                if(!viz[*it]) viz[*it]=1,q.push(*it);
            }
        }
    }
    if(D[Y]!=INF)
        return 1;
    return 0;
}

int main(void){
    register int i,j,x,y,z,c;

    f>>N>>M>>X>>Y;
    for(i=1;i<=M;i++){
        f>>x>>y>>c>>z;
        C[x][y]=c;
        CT[x][y]=z;
        CT[y][x]=-z;
        L[x].push_back(y);
        L[y].push_back(x);
    }

    while(bellmanford()){
        x=Y;
        minim=INF;
        while(T[x]>0) minim=min(minim,C[T[x]][x]-F[T[x]][x]),x=T[x];
        x=Y;
        while(T[x]>0){
            F[T[x]][x]+=minim;
            F[x][T[x]]-=minim;
            x=T[x];
        }
        sol+=minim*D[Y];
    }

    g<<sol;
    f.close();
    g.close();
    return 0;
}