#include <fstream>
#include <vector>
#include <queue>
#pragma GCC optimize("O3")
using namespace std;
ifstream f("fmcm.in");
ofstream g("fmcm.out");
int n,m,st,dr,x,y,z,t;
const int N=355;
int dist[N],d[N][N],flx[N][N];
vector<int>a[N];
int dad[N],ans;
bool viz[N];
int bf()
{
    for(int i=1;i<=n;i++)
        dist[i]=1e9,viz[i]=0;
    dist[st]=    0;
    queue<int>q;
    q.push(st);
    while(!q.empty())
    {
        int nod=q.front();
        q.pop();
        viz[nod]=0;
        for(auto x: a[nod])
            if(flx[nod][x]>0&&dist[x]>dist[nod]+d[nod][x])
            {
                dist[x]=dist[nod]+d[nod][x];
                dad[x]=nod;
                if(viz[x]==0)
                {
                    viz[x]=true;
                    q.push(x);
                }
            }
    }
    return dist[dr];
}
int main()
{
    f>>n>>m>>st>>dr;
    for(int i=1;i<=m;i++)
    {
        f>>x>>y>>z>>t;
        a[x].push_back(y);
        a[y].push_back(x);
        d[x][y]=t;
        d[y][x]=-t;
        flx[x][y]=z;
    }
    while(true)
    {
        int x=bf();
        if(x==1e9)
            break;
            int mn=1e9;
        for(int i=dr;i!=st;i=dad[i])
            mn=min(mn,flx[dad[i]][i]);
        for(int i=dr;i!=st;i=dad[i])
        {
            flx[dad[i]][i]-=mn;
            flx[i][dad[i]]+=mn;
        }
        ans+=mn*x;
    }
    g<<ans;
    return 0;
}