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

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

const int N_MAX=361;
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 f[N_MAX], d[N_MAX];
bool isInPQue[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;
    }
    f[start]=-2;
    d[start]=0;
    for(pQ.push(start); !pQ.empty(); )
    {
        x=pQ.top(); pQ.pop();
        isInPQue[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] > 0)// F[x][it->first])
            {
                f[it->first]=x;
                d[it->first]=d[x]+it->second;
                if(false == isInPQue[it->first])
                {
                    pQ.push(it->first);
                    isInPQue[it->first]=true;
                }
            }
        }
    }
    return -1 != f[end];
}
int main()
{
    long long int sum;
    int N, M, s, e, x, y, c, cMin;
    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));
    }
    for(sum=0; findPath(s, e, N); sum+=1LL*cMin*d[e])
    {
        cMin=oo;
        for(x=e; -2 != f[x]; x=f[x])
            cMin=_min(cMin, C[f[x]][x]);// - F[f[x]][x]);
        for(x=e; -2 != f[x]; x=f[x])
        {
            C[f[x]][x]-=cMin;
            C[x][f[x]]+=cMin;
           /* F[f[x]][x]+=cMin;
            F[x][f[x]]-=cMin; */
        }
    }
    out<<sum<<'\n';

    return EXIT_SUCCESS;
}