#include <bits/stdc++.h>
#include <cstring>
#pragma GCC optimize ("O3")
#define din cin
#define dout out
#define pi 3.14159265359
#define sw(x,y) x^=y,y^=x,x^=y
#define bmin(a,b)((a<b)?(a):(b))
#define bmax(a,b)((a>b)?(a):(b))
#define bminify(a,b)a=bmin(a,b)
#define bmaxify(a,b)a=bmax(a,b)
#define forq(i,ii,n)for(i=ii;i<n;i++)
#define f first
#define s second
#define mod 1000000297ll
#define smax 51000
using namespace std;
typedef long long ll;
//ifstream in("fmcm.in");
//ofstream out("fmcm.out");
FILE *fin=fopen("fmcm.in","r");
FILE *fout=fopen("fmcm.out","w");
int n,m,i,j,k,l,n1,n2,v[351][351][3],d[351],e[351],f[351];vector<int>g[351];
ll c[350000];bitset<351>b;ll tf,tc;
int main()
{
fscanf(fin,"%d%d%d%d",&n,&m,&n1,&n2);
forq(k,0,m)
    fscanf(fin,"%d%d",&i,&j),fscanf(fin,"%d%d",&v[i][j][0],&v[i][j][1]),g[i].push_back(j),g[j].push_back(i),v[j][i][0]=-0,v[j][i][1]=-v[i][j][1];
//forq(i,0,n)for(auto j:g[i])printf("%d %d: %d %d %d %d\n",i,j,v[i][j][0],v[i][j][1],v[j][i][0],v[j][i][1]);
fill(d,d+n+1,INT_MAX/2);
d[n1]=0,c[0]=n1,l=1;
while(l)
{
    if(d[c[0]&1023]!=(c[0]>>10)){pop_heap(c,c+l,greater<ll>()),--l;continue;}
    i=c[0]&1023;pop_heap(c,c+l,greater<ll>()),--l;
    //printf("%d:%d\n",i,d[i]);
    for(auto j:g[i])
        if(v[i][j][0])
            if(d[j]>d[i]+v[i][j][1])
                d[j]=d[i]+v[i][j][1],c[l++]=(d[j]<<10ll)|j,push_heap(c,c+l,greater<ll>());
}
forq(i,1,n+1)for(auto j:g[i])if(v[i][j][0])v[i][j][2]=v[i][j][1]+d[i]-d[j],v[j][i][2]=v[j][i][1]+d[j]-d[i];
while(true)
{
    fill(e,e+n+1,INT_MAX/2);f[n2]=0;
    b[n1]=1,e[n1]=0,l=1,c[0]=(e[n1]<<10ll)|n1;
    while(l)
    {
        i=c[0]&1023;//printf("incerc%d:%d/%d\n",i,e[i],l);
        if(e[i]==c[0]>>10)
        {
            pop_heap(c,c+l,greater<ll>());--l;
            for(auto j:g[i])
                if(v[i][j][0]>0&&e[j]>e[i]+v[i][j][2])
                    //printf("!%d %d %d\n",j,e[j],e[i]+v[i][j][2]),
                    e[j]=e[i]+v[i][j][2],f[j]=i,c[l++]=(e[j]<<10ll)|j,push_heap(c,c+l,greater<ll>());
        }
            else pop_heap(c,c+l,greater<ll>()),--l;
    }
    if(f[n2]==0)break;
    else{
        j=n2,k=INT_MAX;
        while(j!=n1)bminify(k,v[f[j]][j][0]),j=f[j];
        //printf("pa%d\n",k);
        tf+=k,j=n2,i=0;
        while(j!=n1)
            v[f[j]][j][0]-=k,v[j][f[j]][0]+=k,i+=v[f[j]][j][1],j=f[j];
        tc+=i*k;
    }
}
fprintf(fout,"%lld",tc);
fclose(fin),fclose(fout);
}