#include<cstdio>
#include<vector>
#include<deque>
#include<queue>
#include<bitset>

using namespace std;

typedef pair<int,int> PII;
const int INF = (1<<30);
const int NMAX = 355;

struct cmp
{
    bool operator()(PII A,PII B)
    {
        return A.second>B.second;
    }
};

int N,M,Source,Destination,Sol;
vector<int> V[NMAX];
int Capacity[NMAX][NMAX];
int Cost[NMAX][NMAX];
int Flow[NMAX][NMAX];

deque<int> Q;
bitset<NMAX> viz;
int DistBF[NMAX];
int DistDJ[NMAX];
int Dist[NMAX];
int T[NMAX];
priority_queue<PII,vector<PII>,cmp> PQ;

void BellmanFord()
{
    int i,x;
    vector<int>::iterator it;
    for(i=1; i<=N; i++)
        DistBF[i]=INF;

    Q.push_back(Source);
    viz[Source]=1;
    DistBF[Source]=0;

    for(; !Q.empty();)
    {
        x=Q.front();
        Q.pop_front();
        viz[x]=0;

        for(it=V[x].begin(); it!=V[x].end(); it++)
            if(DistBF[x] + Cost[x][*it] < DistBF[*it] && Capacity[x][*it])
            {
                DistBF[*it]=DistBF[x] + Cost[x][*it];
                if(!viz[*it]) Q.push_back(*it);
                viz[*it]=1;
            }
    }
}

bool Dijkstra()
{
    int i,c,x,d;
    vector<int>::iterator it;
    for(i=1; i<=N; i++)
        DistDJ[i]=INF;

    PQ.push(make_pair(Source,0));
    T[Source]=Source;
    DistDJ[Source]=0;

    for(; !PQ.empty();)
    {
        x=PQ.top().first;
        d=PQ.top().second;
        PQ.pop();

        if(d > DistDJ[x]) continue;

        for(it=V[x].begin(); it!=V[x].end(); it++)
            if(Flow[x][*it]<Capacity[x][*it])
            {
                c=Cost[x][*it]+DistBF[*it]-DistBF[x];

                if(DistDJ[x] + c < DistDJ[*it])
                {
                    DistDJ[*it]=DistDJ[x] + c;
                    T[*it]=x;
                    PQ.push(make_pair(*it,DistDJ[*it]));
                    Dist[*it]=Dist[x] + Cost[x][*it];
                }
            }
    }

    for(i=1; i<=N; i++)
        DistBF[i]=Dist[i];

    return DistDJ[Destination]!=INF;
}

int main()
{
    int x,y,c,z,v;

    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);

    scanf("%d%d%d%d",&N,&M,&Source,&Destination);

    for(; M; --M)
    {
        scanf("%d%d%d%d",&x,&y,&c,&z);
        Capacity[x][y]=c;
        Cost[x][y]=z;
        Cost[y][x]=-z;
        V[x].push_back(y);
        V[y].push_back(x);
    }

    BellmanFord();

    for(; Dijkstra();)
    {
        v=INF;

        for(x=Destination; x!=Source; x=T[x])
            v=min(v,Capacity[T[x]][x]-Flow[T[x]][x]);

        for(x=Destination; x!=Source; x=T[x])
        {
            Flow[T[x]][x]+=v;
            Flow[x][T[x]]-=v;
        }

        Sol+=v*DistBF[Destination];
    }

    printf("%d\n",Sol);
    return 0;
}