#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;

struct edge{
    int a,b;
    int cost;
    int capacity;
    int flow;
    edge(){
        a = b = cost = capacity = flow = 0;
    }
    edge(int from,int to, int cost, int capacity, int flow){
        this->a = from;
        this->b = to;
        this->cost = cost;
        this->capacity = capacity;
        this->flow = flow;
    }
}E[30000];
int nr = -1,N,M,S,D;
int DP[Nmax],daddy[Nmax];
vector<pair<int,int> > G[Nmax];
bitset<Nmax>inQ;
queue<int> Q;

void Insert(int a, int b, int cost,int capacity)
{
    E[++nr] = edge(a,b,cost,capacity,0);
    G[a].push_back(make_pair(b,nr));
}

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<pair<int,int> >::iterator it = G[k].begin(); it != G[k].end(); ++it)
            if(DP[it->v] > DP[k] + E[it->e].cost && E[it->e].flow != E[it->e].capacity)
            {
                DP[it->v] = DP[k] + E[it->e].cost;
                daddy[it->v] = it->e;
                if(inQ[it->v]) continue;
                inQ[it->v] = 1;
                Q.push(it->v);
            }
    }
    return (DP[sink] != INF);
}

void FLOW(int k)
{
    int minFLOW,maxFLOW = 0,minCOST = 0;
    while(bellman_ford(k))
    {
        if(E[daddy[sink]].capacity - E[daddy[sink]].flow == 0) continue;
        minFLOW = INF;
        for(int nodc = sink; nodc != start; nodc = E[daddy[nodc]].a + E[daddy[nodc]].b - nodc)
            minFLOW = min (minFLOW, E[daddy[nodc]].capacity - E[daddy[nodc]].flow);
        if(minFLOW == 0) continue;
        for(int nodc = sink; nodc != start; nodc = E[daddy[nodc]].a + E[daddy[nodc]].b - nodc)
        {
            E[daddy[nodc]].flow += minFLOW;
            E[daddy[nodc]^1].flow -= 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;
}