#include <cstdio>
#include <algorithm>
#include <bitset>
#include <vector>
#include <cstring>
#include <queue>

#define start S
#define sink D
#define v first
#define e second

#define Nmax 400
#define INF 0x3f3f3f3f

using namespace std;

int nr = -1,N,M,S,D;
int DP[Nmax],daddy[Nmax],cost[Nmax][Nmax],capacity[Nmax][Nmax],flow[Nmax][Nmax];
vector<int> G[Nmax];
bitset<Nmax>inQ;
queue<int> Q;

void Insert(int a, int b, int cst,int capac)
{
    capacity[a][b] = capac;
    cost[a][b] = cst;
    flow[a][b] = 0;
    G[a].push_back(b);
}

void read( void )
{
    scanf("%d%d%d%d",&N,&M,&S,&D);
    int a,b,cap,cost;
    for(int i = 1; i <= M; ++i){
        scanf("%d%d%d%d",&a,&b,&cap,&cost);
        Insert(a,b,cost,cap);
        Insert(b,a,-cost,0);
    }
}

bool bellman_ford(int k)
{
    memset(DP,INF,sizeof(DP));
    DP[k] = 0;
    inQ = 0;
    Q.push(k);
    while(!Q.empty()){
        k = Q.front(); Q.pop(); inQ[k] = 0;
        if(k == sink) continue;
        for(vector<int>::iterator it = G[k].begin(); it != G[k].end(); ++it)
            if(DP[*it] > DP[k] + cost[k][*it] && capacity[k][*it] != flow[k][*it])
            {
                DP[*it] = DP[k] + cost[k][*it];
                daddy[*it] = k;
                if(inQ[*it]) continue;
                inQ[*it] = 1;
                Q.push(*it);
            }
    }
    return (DP[sink] != INF);
}

void FLOW(int k)
{
    int minFLOW,maxFLOW = 0,minCOST = 0;
    while(bellman_ford(k))
    {
        if(capacity[daddy[sink]][sink] - flow[daddy[sink]][sink] == 0 || DP[sink] == INF) continue;
        minFLOW = INF;
        for(int nodc = sink; nodc != start; nodc = daddy[nodc])
            minFLOW = min (minFLOW,capacity[daddy[nodc]][nodc] - flow[daddy[nodc]][nodc]);
        if(minFLOW == 0) continue;
        for(int nodc = sink; nodc != start; nodc = daddy[nodc])
        {
            flow[daddy[nodc]][nodc] += minFLOW;
            flow[nodc][daddy[nodc]] -= minFLOW;
        }
        minCOST += minFLOW * DP[sink];
        maxFLOW += minFLOW;
    }
    printf("%d\n",minCOST);
}

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

    read();
    FLOW(start);

    return 0;
}