#include <bits/stdc++.h>

using namespace std;

const int inf=1e9;
struct edge
{
    int nod,c;
    bool operator <(const edge &aux) const
    {
        return c>aux.c;
    }
};
vector<edge> g[355];
priority_queue<edge> h;
queue<int> q;
int cap_flow[355][355],dist[355],dist1[355],d[355],tata[355],n,sursa,dest;
char vaz[355];

void bellman_ford()
{
    for(int i=1;i<=n;i++) dist[i]=inf;
    q.push(sursa);
    dist[sursa]=0;
    vaz[sursa]=1;
    while(!q.empty())
    {
        int nod=q.front();
        q.pop();
        vaz[nod]=0;
        for(vector<edge>::iterator it=g[nod].begin();it!=g[nod].end();it++)
            if(cap_flow[nod][it->nod] && dist[nod]+it->c<dist[it->nod])
            {
                dist[it->nod]=dist[nod]+it->c;
                if(it->nod!=dest && !vaz[it->nod])
                {
                    q.push(it->nod);
                    vaz[it->nod]=1;
                }
            }
    }
}

int dijkstra()
{
    for(int i=1;i<=n;i++) d[i]=dist1[i]=inf;
    d[sursa]=dist1[sursa]=0;
    h.push({sursa,0});
    while(!h.empty())
    {
        int nod=h.top().nod,c=h.top().c;
        h.pop();
        if(d[nod]!=c) continue;
        for(vector<edge>::iterator it=g[nod].begin();it!=g[nod].end();it++)
            if(cap_flow[nod][it->nod] && d[nod]+dist[nod]+it->c-dist[it->nod]<d[it->nod])
            {
                d[it->nod]=d[nod]+dist[nod]+it->c-dist[it->nod];
                dist1[it->nod]=dist1[nod]+it->c;
                tata[it->nod]=nod;
                if(it->nod!=dest) h.push({it->nod,d[it->nod]});
            }
    }
    for(int i=1;i<=n;i++) dist[i]=dist1[i];
    return d[dest]<inf;
}

int main()
{
    freopen("file.in", "r" ,stdin);
    freopen("file.out", "w", stdout);
    int m,sol=0;
    scanf("%d%d%d%d",&n,&m,&sursa,&dest);
    for(int i=1;i<=m;i++)
    {
        int x,y,c,s;
        scanf("%d%d%d%d",&x,&y,&c,&s);
        g[x].push_back({y,s});
        g[y].push_back({x,-s});
        cap_flow[x][y]=c;
    }
    bellman_ford();
    while(dijkstra())
    {
        int s=inf;
        for(int nod=dest;nod!=sursa;nod=tata[nod]) s=min(s,cap_flow[tata[nod]][nod]);
        for(int nod=dest;nod!=sursa;nod=tata[nod])
        {
            cap_flow[tata[nod]][nod]-=s;
            cap_flow[nod][tata[nod]]+=s;
        }
        sol+=s*dist[dest];
    }
    printf("%d",sol);
    return 0;
}