#include<bits/stdc++.h>
using namespace std;

#define N 360
#define fi first
#define se second
#define INF 0x3f3f3f3f

vector<int> v[N];
int adj[N][N], n, m, s, d, path[N], cost[N][N], dist[N], false_dist[N];
bool in_queue[N];

void bellmanford(){
    queue<int> q;
    vector<bool> in_queue(n+2, 0);

    for(int i = 1;i<=n;i++){
        dist[i] = INF;
    }
    dist[s] = 0;
    q.push(s);
    in_queue[s] = 1;

    while(!q.empty()){
        int curr = q.front();
        q.pop();
        in_queue[curr] = 0;
        for(auto next: v[curr]){
            if(adj[curr][curr] && dist[next] > dist[curr] + cost[curr][next]){
                dist[next] = dist[curr] + cost[curr][next];
                if(!in_queue[next]){
                    q.push(next);
                    in_queue[next] = 1;
                }
            }
        }
    }
}

struct cmp{
    bool operator() (int i, int j) const{
        return false_dist[i] > false_dist[j];
    }
};
priority_queue <int, vector<int>, cmp> q;
bool dijkstra(){


    for(int i = 1;i<=n;i++){
        false_dist[i] = INF;
        in_queue[i] = 0;
        path[i] = 0;
    }

    false_dist[s] = 0;
    path[s] = -1;

    q.push(s);
    in_queue[s] = 1;
    while(!q.empty()){
        int curr = q.top();
        q.pop();
        in_queue[curr] = 0;
        for(auto next: v[curr]){
            if(adj[curr][next] && false_dist[next] > false_dist[curr] + cost[curr][next] + dist[curr] - dist[next]){
                false_dist[next] = false_dist[curr] + cost[curr][next] + dist[curr] - dist[next];
                path[next] = curr;
                if(!in_queue[next]){
                    in_queue[next] = 1;
                    q.push(next);
                }
            }
        }
    }
    return path[d];
}

long long mfmc(){
    long long ans = 0;
    while(dijkstra()){

        int curr = d;
        long long flow = INF;
        while(path[curr] != -1){
            if(flow < adj[path[curr]][curr])
                flow = adj[path[curr]][curr];
            curr = path[curr];
        }
        curr = d;
        while(path[curr] != -1){
            adj[path[curr]][curr] -= flow;
            adj[curr][path[curr]] += flow;
            ans+=flow*cost[path[curr]][curr];
            curr = path[curr];
        }
    }
    return ans;
}

int main(){

    ifstream cin("fmcm.in");
    ofstream cout("fmcm.out");

    cin>>n>>m>>s>>d;
    for(int i = m;i;i--){
        int a,b,c,z;
        cin>>a>>b>>c>>z;
        v[a].push_back(b);
        v[b].push_back(a);
        adj[a][b] = c;
        cost[a][b] = z;
        cost[b][a] = -z;
    }

    bellmanford();
    cout<<mfmc();

    return 0;
}