#include <fstream>
#include <bitset>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;
ifstream fin("fmcm.in");
ofstream fout("fmcm.out");
const int N=351,inf=0x3f3f3f3f;
int dist[N],C[N][N],cost[N][N],n,m,s,d,flux,tata[N];
long long costflux;
vector<int>H[N];
vector<int>::iterator it;
bitset<N>viz;
queue<int>Q;
bool bellmanford()
{
    viz.reset();
    memset(dist,inf,sizeof(dist));
    memset(tata,-1,sizeof(tata));
    viz[s]=1;
    dist[s]=0;
    Q.push(s);
    while(Q.size())
    {
        int nod=Q.front();
        Q.pop();
        for(it=H[nod].begin();it!=H[nod].end();it++)
        {
            if(C[nod][*it] && (dist[*it]>dist[nod]+cost[nod][*it]))
            {
                tata[*it]=nod;
                dist[*it]=dist[nod]+cost[nod][*it];
                Q.push(*it);
            }
        }
    }
    if(dist[d]==inf) return 0;
    int fmin=inf;
    for(int i=d;i!=s;i=tata[i])
    {
        fmin=min(fmin,C[tata[i]][i]);
    }
    for(int i=d;i!=s;i=tata[i])
    {
        C[tata[i]][i]-=fmin;
        C[i][tata[i]]+=fmin;
    }
    costflux+=fmin*dist[d];
    return 1;
}
int main()
{
    int i,a,b,c,z;
    fin>>n>>m>>s>>d;
    for(i=1;i<=m;i++)
    {
        fin>>a>>b>>c>>z;
        H[a].push_back(b);
        H[b].push_back(a);
        C[a][b]=c;
        cost[a][b]=z;
        cost[b][a]=-z;
    }
    while(bellmanford());
    fout<<costflux;
}