#include<fstream>
#include<vector>
#include<queue>
#include<cstring>
using namespace std;
#define INF 0x3f3f3f3f
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
vector <int> v[355];
queue <int> q;
int n,m,s,d,x,y,z,p,c,dh,minim,cost;
int D[355],R[355],E[355],T[355],H[355],P[355],C[355][355],F[355][355],Z[355][355];
void bellman_ford()
{
    int i;
    memset(D,0x3f,sizeof(D));
    D[s]=0;
    q.push(s);
    while (!q.empty())
    {
        x=q.front(); q.pop();
        for (i=0;i<v[x].size();++i)
        {
            y=v[x][i], z=Z[x][y];
            if (D[y]>D[x]+z && C[x][y]>F[x][y])
            {
                D[y]=D[x]+z;
                q.push(y);
            }
        }
    }
}
bool dijkstra()
{
    int i,aux;
    memset(T,0,sizeof(T));
    memset(E,0x3f,sizeof(E));
    R[s]=0, E[s]=0;
    H[dh=1]=s, P[s]=1;
    while (dh>0)
    {
        x=H[1];
        H[1]=H[dh--];
        P[H[1]]=1, P[x]=0;
        p=1, c=2;
        while (c<=dh)
        {
            if (c<dh && E[H[c+1]]<E[H[c]])
                ++c;
            if (E[H[p]]>E[H[c]])
            {
                aux=H[p], H[p]=H[c], H[c]=aux;
                P[H[p]]=p, P[H[c]]=c;
            }
            else
                break;
            p=c, c=p<<1;
        }
        for (i=0;i<v[x].size();++i)
        {
            y=v[x][i];
            if (E[y]>E[x]+Z[x][y]+D[x]-D[y] && C[x][y]>F[x][y])
            {
                E[y]=E[x]+Z[x][y]+D[x]-D[y];
                R[y]=R[x]+Z[x][y];
                T[y]=x;
                if (P[y])
                    c=P[y];
                else
                {
                    H[++dh]=y, c=dh;
                    P[H[dh]]=dh;
                }
                p=c>>1;
                while (p>0)
                {
                    if (E[H[p]]>E[H[c]])
                    {
                        aux=H[p], H[p]=H[c], H[c]=aux;
                        P[H[p]]=p, P[H[c]]=c;
                    }
                    else
                        break;
                    c=p, p=c>>1;
                }
            }
        }
    }
    memcpy(D,R,sizeof(D));
    return (E[d]!=INF);
}
int main()
{
    int i;
    fin>>n>>m>>s>>d;
    for (i=1;i<=m;++i)
    {
        fin>>x>>y>>c>>z;
        v[x].push_back(y);
        v[y].push_back(x);
        C[x][y]=c;
        Z[x][y]=z, Z[y][x]=-z;
    }
    bellman_ford();
    while (dijkstra())
    {
        minim=INF, x=d;
        while (x!=s)
        {
            minim=min(minim,C[T[x]][x]-F[T[x]][x]);
            x=T[x];
        }
        x=d;
        while (x!=s)
        {
            F[T[x]][x]+=minim, F[x][T[x]]-=minim;
            x=T[x];
        }
        cost+=D[d]*minim;
    }
    fout<<cost<<"\n";
    return 0;
}