#include <stdio.h>
#include <vector>
#include <queue>
#include <string.h>
#define inf 10000000
using namespace std;
int n,m,i,k,x,y,z,d[705],t[705],f[705][705],c[705][705],r,cost,j,s,dv[705],dn[705],D,e;
bool o[705];
vector<pair<int,int> > G[705];
queue<int> Q;
class comp
{
public:
    bool operator()(int a,int b)
    {
        return d[a]>d[b];
    }
};
priority_queue<int,vector<int>,comp> H;
void citire()
{
    int i,cp;
    scanf("%i%i%i%i",&n,&m,&s,&e);
    for (i=1;i<=m;i++)
    {
        scanf("%i%i%i%i",&x,&y,&cp,&z);
        c[x][y]=cp;
        G[x].push_back(make_pair(y,z));
        G[y].push_back(make_pair(x,-z));
    }
}
void bellmanford()
{
    int i,z,x,y;
    for (i=1;i<=e;i++)
    {o[i]=0; dv[i]=inf;}
    Q.push(s); o[s]=1; dv[s]=0;
    while (!Q.empty())
    {
        x=Q.front();
        Q.pop(); o[x]=0;
        z=G[x].size();
        for (i=0;i<z;i++)
        {
            y=G[x][i].first;
            if (c[x][y]-f[x][y]>0&&dv[y]>dv[x]+G[x][i].second)
            {
                dv[y]=dv[x]+G[x][i].second;
                if (!o[y])
                {
                    Q.push(y);
                    o[y]=1;
                }
            }
        }
    }
}
int dijkstra()
{
    int i,z,x,y;
    for (i=1;i<=e;i++) {d[i]=inf; t[i]=0;}
    Q.push(s); d[s]=0; dn[s]=0;
    while (!Q.empty())
    {
        x=Q.front();
        Q.pop();
        z=G[x].size();
        for (i=0;i<z;i++)
        {
            y=G[x][i].first;
            D=d[x]+G[x][i].second+dv[x]-dv[y];
            if (c[x][y]-f[x][y]>0&&d[y]>D)
            {
                d[y]=D;
                dn[y]=dn[x]+G[x][i].second;
                t[y]=x;
                Q.push(y);
            }
        }
    }
    memcpy(dv,dn,sizeof(dn));
    return t[e];
}
int main()
{
    freopen ("fmcm.in","r",stdin);
    freopen ("fmcm.out","w",stdout);
    citire();
    bellmanford();
    while (dijkstra())
    {
        r=inf;
        for (i=e;i!=s;i=t[i]) r=min(r,c[t[i]][i]-f[t[i]][i]);
        cost+=r*dn[e];
        for (i=e;i!=s;i=t[i])
        {
            f[t[i]][i]+=r;
            f[i][t[i]]-=r;
        }
    }
    printf("%i",cost);
    fclose(stdin);
    fclose(stdout);
    return 0;
}