#include <stdio.h>
#include <vector>
#include <queue>

#define NMAX 505
#define INF 0x3f3f3f3f

using namespace std;

vector<int> G[NMAX];
queue<int> Q;
bool viz[NMAX];

int N,M,START,DEST;
int A[NMAX][NMAX],F[NMAX][NMAX],C[NMAX][NMAX];
int D[NMAX],P[NMAX];
int OK,MIN;
long long VAL;

void read()
{
    scanf("%d %d %d %d\n",&N,&M,&START,&DEST);

    for (int i=1;i<=M;i++)
    {
        int x,y,c,cost;

        scanf("%d %d %d %d\n",&x,&y,&c,&cost);

        G[x].push_back(y);
        G[y].push_back(x);

        A[x][y]=cost;
        A[y][x]=-cost;
        C[x][y]=c;
    }
}

int BF()
{
    for (int i=1;i<=N;i++)
    {
        D[i]=INF;
        P[i]=0;
        viz[i]=0;
    }

    Q.push(START);
    D[START]=0;
    viz[START]=1;

    while (!Q.empty())
    {
        int node=Q.front();
        Q.pop();
        viz[node]=0;

        for (int i=0;i<G[node].size();i++)
            if (F[node][G[node][i]]<C[node][G[node][i]] && D[node]+A[node][G[node][i]]<D[G[node][i]])
            {
                D[G[node][i]]=D[node]+A[node][G[node][i]];
                P[G[node][i]]=node;

                if (!viz[G[node][i]])
                {
                    viz[G[node][i]]=1;
                    Q.push(G[node][i]);
                }
            }
    }

    if (D[DEST]!=INF)
    {
        OK=1;
        MIN=INF;

        for (int i=DEST;i!=START;i=P[i])
            MIN=min(MIN,C[P[i]][i]-F[P[i]][i]);
        for (int i=DEST;i!=START;i=P[i])
        {
            F[P[i]][i]+=MIN;
            F[i][P[i]]-=MIN;
        }

        return MIN*D[DEST];
    }

    return 0;
}

void solve()
{
    OK=1;

    while (OK)
    {
        OK=0;
        VAL+=BF();
    }

    printf("%lld\n",VAL);
}

int main()
{
    freopen ("fmcm.in","r",stdin);
    freopen ("fmcm.out","w",stdout);

    read();
    solve();

    fclose(stdin);
    fclose(stdout);

    return 0;
}