#include <queue>
#include <fstream>
#include <cstdlib>

using namespace std;
typedef pair<int, int> pr;

const int N_MAX=1011;
const int oo=1<<29;

vector<pr> G[N_MAX];
vector<pr>::const_iterator it, iend;
int C[N_MAX][N_MAX], F[N_MAX][N_MAX];
int d[N_MAX], f[N_MAX];
bool isInQue[N_MAX];
struct cmp {
    bool operator() (const int& x, const int& y) const {return d[x] > d[y];}
};
priority_queue<int, vector<int>, cmp> pQ;
inline int _min(int x, int y) {return x <= y ? x : y;}
bool findPath(int start, int end, int N)
{
    int x;

    for(x=1; x <= N; ++x)
        f[x]=-1, d[x]=oo, isInQue[x]=false;
    f[start]=-2; d[start]=0;
    for(pQ.push(start); !pQ.empty();)
    {
        x=pQ.top(); pQ.pop();
        isInQue[x]=false;
        for(it=G[x].begin(), iend=G[x].end(); it <iend; ++it)
        {
            if(start == it->first)
                continue;
            if(d[it->first] > d[x] + it->second && C[x][it->first] > F[x][it->first])
            {
                d[it->first]=it->second + d[x];
                f[it->first]=x;
                if(false == isInQue[it->first])
                {
                    pQ.push(it->first);
                    isInQue[it->first]=true;
                }
            }
        }
    }
    return -1 != f[end] && oo != d[end];
}
int main()
{
    int N, M, s, e, x, y, c, cMin, sum=0;
    ifstream in("fmcm.in");
    ofstream out("fmcm.out");

    for(in>>N>>M>>s>>e; M; --M)
    {
        in>>x>>y;
        in>>C[x][y]>>c;
        G[x].push_back(pr(y, c));
        G[y].push_back(pr(x, -c));
    }
    while(findPath(s, e, N))
    {
        cMin=oo;
        for(x=N; -2 != f[x]; x=f[x])
            cMin=_min(cMin, C[f[x]][x] - F[f[x]][x]);
        for(x=N; -2 != f[x]; x=f[x])
        {
            F[f[x]][x]+=cMin;
            F[x][f[x]]-=cMin;
        }
        sum+=cMin*d[e];
    }
    out<<sum<<'\n';
    return EXIT_SUCCESS;
}