#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<queue>
using namespace std;

#define NMAX 352
#define INF 2000000000

int n,m,d,s,mini=2000;
int f[NMAX][NMAX],t[NMAX],val[NMAX],cost[NMAX][NMAX];
bool fv[NMAX][NMAX];

struct nodc
{
    int x,c;
}nod,fiu;

vector<int>v[NMAX];

struct cmp
{
    bool operator()(const nodc &a,const nodc &b)
    {
        return a.c>b.c;
    }
};

priority_queue<nodc,vector<nodc>, cmp> q;

bool drum()
{
    int i;

    memset(t,0,sizeof(t));
    for(i=0;i<NMAX;++i)
        val[i]=-INF;
    while(!q.empty())
        q.pop();

    nod.x=s;
    nod.c=0;
    q.push(nod);

    t[s]=s;
    val[s]=mini;

    while(!q.empty())
    {
        nod=q.top();
        q.pop();

        for(i=0;i<v[nod.x].size();++i)
        {
            fiu.x=v[nod.x][i];
            fiu.c=nod.c+cost[nod.x][fiu.x];

            if(f[fiu.x][nod.x] && t[fiu.x]==0 && (val[fiu.x]==-INF ||val[fiu.x]>fiu.c))
            {
                val[fiu.x]=fiu.c;
                t[fiu.x]=nod.x;
                if(fiu.x == d)
                    return 1;

                q.push(fiu);
            }
        }
    }
    return 0;
}

int main()
{
    freopen("fmcm.in","r",stdin);
    freopen("fmcm.out","w",stdout);
    int i,j,x,y,cap,ct,maxc,sol=0;

    scanf("%d%d%d%d",&n,&m,&s,&d);
    for(i=1;i<=m;++i)
    {
        scanf("%d%d%d%d",&x,&y,&cap,&ct);
        v[x].push_back(y);
        v[y].push_back(x);

        f[y][x]=cap;
        cost[x][y]=ct;
        cost[y][x]=-ct;

        if(ct<mini)mini=ct;
        if(-ct<mini)mini=-ct;
    }
    if(mini<0)
    {
        mini=-mini+1;
        for(i=1;i<=n;++i)
            for(j=i+1;j<=n;++j)
            {
                cost[i][j]+=mini;
                cost[j][i]+=mini;
            }
    }else
        mini=0;

     while(drum())
    {
        maxc=INF;
        for(i=d;i!=s;i=t[i])
            if(f[i][t[i]]<maxc)
                maxc=f[i][t[i]];

        for(i=d;i!=s;i=t[i])
        {
            f[i][t[i]]-=maxc;
            f[t[i]][i]+=maxc;

            if(!fv[t[i]][i])
            {
                fv[t[i]][i]=1;
                //sol+=cost[t[i]][i]-mini;
            }
        }

        sol+=maxc;
    }

    printf("%d\n",sol);

    return 0;
}