#include <fstream>
#include <vector>
#include <queue>
using namespace std;

const int N=351,inf=1<<30;
int cap[N][N],cost[N][N],flux[N][N],dist[N],T[N],n;
class compare
{
    public:
    bool operator()(const int &a,const int &b)
    {
        return dist[a]<dist[b];
    }
};
queue <int> Q;
vector<int> a[N];

ifstream in("fmcm.in");
ofstream out("fmcm.out");

inline int dif(int x,int y)
{
    return cap[x][y]-flux[x][y];
}

bool bf(int x,int D)
{
    for (int i=1;i<=n;i++)
        dist[i]=inf;
    while (!Q.empty())
        Q.pop();
    dist[x]=0;
    Q.push(x);
    while (!Q.empty())
    {
        x=Q.front();Q.pop();
        if (x==D)
            continue;
        for (vector<int>::iterator i=a[x].begin();i!=a[x].end();i++)
            if (dif(x,*i)>0 && dist[x]+cost[x][*i]<dist[*i])
            {
                dist[*i]=dist[x]+cost[x][*i];
                T[*i]=x;
                Q.push(*i);
            }
    }
    return dist[D]!=inf;
}

int flow(int S,int D)
{
    int C=0,M;
    while (bf(S,D))
    {
        M=inf;
        for (int i=D;i!=S;i=T[i])
            M=min(M,dif(T[i],i));
        if (!M)
            break;
        for (int i=D;i!=S;i=T[i])
        {
            flux[T[i]][i]+=M;
            flux[i][T[i]]-=M;
        }
        C+=M*dist[D];
    }
    return C;
}

int main()
{
    int m,x,y,c,z,S,D;
    in>>n>>m>>S>>D;
    while (m--)
    {
        in>>x>>y>>c>>z;
        a[x].push_back(y);
        a[y].push_back(x);
        cap[x][y]=c;
        cost[x][y]=z;
        cost[y][x]=-z;
    }
    out<<flow(S,D)<<"\n";
    return 0;
}