#include <bits/stdc++.h>

using namespace std;

#define MAXN 355

int n , m , s , D ,aaa;
int x , y ;
int cap[MAXN][MAXN];
int cst[MAXN][MAXN];
int f , fcst ;
int old_d[MAXN];
int   inQ[MAXN];
int     d[MAXN];
int   r_d[MAXN];
int     p[MAXN];
vector<int> con[MAXN];
vector<int> :: iterator it;
queue<int> q;
priority_queue<pair<int, int>, vector<pair<int, int> >, greater<pair<int, int> > > h;

void bellmanford(){
    memset(old_d , 0x3f , sizeof(old_d));

    old_d [s] = 0;
    inQ   [s] = 1;

    q.push(s);
    for(; !q.empty(); q.pop() ){
        int i = q.front();
        inQ[i]= 0;
        for(it = con[i].begin() ; it != con[i].end(); ++it)
            if( cap[i][*it] ){

                if( old_d[i] + cst[i][*it] >= old_d[*it] ) continue;
                old_d[*it] = old_d[i] + cst[i][*it];

                if( inQ[*it] ) continue;

                inQ[*it] = 1;
                q.push(*it);
            }
    }
}

bool dijkstra(){
    memset(d , 0x3f , sizeof(d));
    r_d[s] = 0;
      d[s] = 0;

    h.push( make_pair( d[s] , s ) );
    for( ; !h.empty();   ){
        int cost = h.top().first , nod = h.top().second;
        h.pop();
        if( d[nod] != cost ) continue;
        for(it = con[nod].begin() ; it != con[nod].end(); ++it  ){
            aaa = *it;
            if( cap[nod][*it] ){
                int new_d = d[nod] + cst[nod][*it] + old_d[nod] - old_d[*it];
                if( new_d < d[*it] ){
                    d[*it] = new_d;
                    r_d[*it] = r_d[nod] + cst[nod][*it];
                    p[*it] = nod;
                    h.push( make_pair(d[*it] , *it) );
                }
            }
        }
    }
     memcpy(old_d, r_d, sizeof(d));
     if (d[D] == 0x3f3f3f3f)
        return false;
    int Min = 0x3f3f3f3f, curCst = 0;
     for (int aux = D; aux != s; aux = p[aux])
        Min = min(Min, cap[p[aux]][aux]),
        curCst += cst[p[aux]][aux];

    f += Min;
    fcst += Min * r_d[D];
    for (int aux = D; aux != s; aux = p[aux])
        cap[p[aux]][aux] -= Min,
        cap[aux][p[aux]] += Min;

    return true;
}


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

    scanf("%d %d %d %d",&n,&m,&s,&D);

    for( ; m ; --m ){
        scanf("%d %d ", &x,&y);
        con[x].push_back(y);
        con[y].push_back(x);
        scanf("%d %d ",&cap[x][y] , &cst[x][y]);
        cst[y][x] = -cst[x][y];
    }

    bellmanford();
    while(true){
        if( dijkstra() ) continue;
        break;

    }

    printf("%d\n", fcst);

    return 0;
}