#include <stdio.h>
#include <vector>
#include<cstring>
using namespace std;
#define maxn 510
#define inf 2000000000
#define ll long long
#define maxx 1000010
int N, M, S, D;
int Drum, L;
vector <int> A[maxn];
int G[maxn], Dist[maxn], From[maxn];
int Q[maxx], U[maxn];
int C[maxn][maxn], F[maxn][maxn], Cost[maxn][maxn];
int BellmanFord()
{
int i, j;
for (i = 1; i <= N; i++)
{
Dist[i] = inf;
From[i] = -1;
}
Dist[S] = 0;
L = 1;
Q[L] = S;
memset(U, 0, sizeof(U));
U[S] = 1;
for (i = 1; i <= L; i++)
{
for (j=0; j<G[Q[i]]; j++)
if (C[Q[i]][A[Q[i]][j]]-F[Q[i]][A[Q[i]][j]]>0 && Dist[Q[i]]+Cost[Q[i]][A[Q[i]][j]]<Dist[A[Q[i]][j]])
{
Dist[A[Q[i]][j]] = Dist[Q[i]] + Cost[Q[i]][A[Q[i]][j]];
From[A[Q[i]][j]] = Q[i];
if (!U[A[Q[i]][j]])
{
Q[++L] = A[Q[i]][j];
U[Q[L]] = 1;
}
}
U[Q[i]] = 0;
}
if (Dist[D] != inf)
{
int Vmin = inf;
Drum = 1;
for (i = D; i != S; i = From[i]) Vmin = min(Vmin, C[From[i]][i] - F[From[i]][i]);
for (i = D; i != S; i = From[i])
{
F[From[i]][i] += Vmin;
F[i][From[i]] -= Vmin;
}
return Vmin * Dist[D];
}
return 0;
}
ll Flux()
{
ll Rez = 0;
Drum = 1;
while (Drum)
{
Drum = 0;
Rez += BellmanFord();
}
return Rez;
}
int main()
{
freopen("fmcm.in", "r", stdin);
freopen("fmcm.out", "w", stdout);
int i, x, y, z, cap;
scanf("%d %d %d %d ", &N, &M, &S, &D);
for (i = 1; i <= M; i++)
{
scanf("%d %d %d %d ", &x, &y, &cap, &z);
A[x].push_back(y);
A[y].push_back(x);
C[x][y] = cap;
Cost[x][y] = z;
Cost[y][x] = -z;
}

for (i = 1; i <= N; i++) G[i] = A[i].size();
printf("%lld\n", Flux());
return 0;
}