#include<fstream>
#include<list>
#include<vector>
#include<algorithm>
#include<cstring>
#define DMAX 351
#define INF 0x3f3f3f3f
using namespace std;

ifstream fin ("fmcm.in");
ofstream fout("fmcm.out");
list<int> lista;
list<int>::iterator it;
vector< list<int> >l(DMAX,lista);
int n,m,x,y,c,z,s,d,flxmin,flux,i;
int flx[DMAX][DMAX],cost[DMAX][DMAX],cap[DMAX][DMAX],viz[DMAX],dad[DMAX],que[DMAX],dist[DMAX];

int f()
{
    int ls=0,ld=0;
    for(i=1;i<=n;++i)
    {
        viz[i]=dad[i]=0;
        dist[i]=INF;
    }
    que[0]=s; viz[s]=1; dist[s]=0;
    while(ls<=ld)
    {
        x=que[ls++];
        for(it=l[x].begin();it!=l[x].end();++it)
        {
            y=*it;
            if(cap[x][y]>flx[x][y] && dist[y]>dist[x]+cost[x][y])
            {
                dist[y]=dist[x]+cost[x][y];
                dad[y]=x;
                if(!viz[y])
                {
                    que[++ld]=y;
                    viz[y]=1;
                }
            }
        }
        viz[x]=0;
    }
    if(dist[d]==INF)
        return 0;
    flux=INF;
    for(i=d;i!=s;i=dad[i])
        flux=min(flux,cap[dad[i]][i]-flx[dad[i]][i]);
    if(flux!=INF)
    {
        for(i=d;i!=s;i=dad[i])
        {
            flx[dad[i]][i]+=flux;
            flx[i][dad[i]]-=flux;
        }
        flxmin+=flux*dist[d];
    }
    return 1;
}

int main()
{
    fin>>n>>m>>s>>d;
    for(i=1;i<=m;++i)
    {
        fin>>x>>y>>c>>z;
        l[x].push_back(y);
        l[y].push_back(x);
        cap[x][y]=c;
        cost[x][y]=z;
        cost[y][x]=-z;
    }
    while(f());
    fout<<flxmin;
    return 0;
}