#include <bits/stdc++.h>

using namespace std;

ifstream f("fmcm.in");
ofstream g("fmcm.out");

int n,m,S,D,i,j,x,y,c,z,flxmax,d[360],real_d[360],tata[360],dist[360],cap[360][360],cost[360][360];
vector<int> v[360];

void bellman()
{
    memset(dist,127,sizeof(dist));
    bitset<360> in;in.reset();
    dist[S]=0;in[S]=1;
    queue<int> q;
    q.push(S);
    while(q.size())
    {
        int x=q.front();q.pop();in[x]=0;
        for(auto it:v[x])
            if(cap[x][it])
                if(dist[it]>dist[x]+cost[x][it])
                {
                    dist[it]=dist[x]+cost[x][it];
                    if(!in[it])
                        q.push(it);
                    in[it]=1;
                }
    }
}

bool djikstra()
{
    memset(d,127,sizeof(d));
    memset(real_d,127,sizeof(real_d));
    memset(tata,0,sizeof(tata));
    priority_queue<pair<int,int> > q;
    d[S]=real_d[S]=0;
    q.push({0,S});
    while(q.size())
    {
        int y=-q.top().first,x=q.top().second;
        q.pop();if(y>d[x])continue;
        for(auto it:v[x])
            if(cap[x][it])
                if(d[it]>d[x]+cost[x][it]+dist[x]-dist[it])
                {
                    d[it]=d[x]+cost[x][it]+dist[x]-dist[it];
                    real_d[it]=real_d[x]+cost[x][it];
                    q.push({-d[it],it});tata[it]=x;
                }
    }
    for(i=1;i<=n;i++)
        dist[i]=real_d[i];
    if(dist[D]>1e9)return 0;
    int ke=1e9;
    for(int x=D;tata[x];x=tata[x])
        ke=min(ke,cap[tata[x]][x]);
    for(int x=D;tata[x];x=tata[x])
        cap[tata[x]][x]-=ke,cap[x][tata[x]]+=ke;
    flxmax+=ke*dist[D];
    return 1;
}

int main()
{
    f>>n>>m>>S>>D;
    for(i=1;i<=m;i++)
    {
        f>>x>>y>>c>>z;
        v[x].push_back(y);
        v[y].push_back(x);
        cap[x][y]=c;
        cost[x][y]=z;
        cost[y][x]=-z;
    }
    bellman();
    for(;djikstra(););
    g<<flxmax;
    return 0;
}