#include<bits/stdc++.h>
// 9:46

#define f first
#define s second
#define pb push_back
#define ll long long
#define sz(x) (int)(x).size()
#define all(x) (x).begin(),(x).end()

using namespace std;

struct edge{
    int a,b;ll cap;
};
const int N=2005;
const ll oo=LLONG_MAX/2;
int s=N-2,t=N-1;
vector<edge> e;
vector<int> graf[N];
int start[N],level[N];
void addEdge(int u,int v,ll cap){
    graf[u].pb(sz(e));
    e.pb({u,v,cap});
    graf[v].pb(sz(e));
    e.pb({v,u,0});
}
bool bfs(){
    memset(level,-1,sizeof(level));
    queue<int> q;
    q.push(s);
    level[s]=0;
    while(sz(q)){
        int tr=q.front();
        q.pop();
        for(auto p:graf[tr]){
            if(e[p].cap==0||level[e[p].b]!=-1)continue;
            level[e[p].b]=level[tr]+1;
            q.push(e[p].b);
        }
    }
    return level[t]!=-1;
}
ll dfs(int tr,ll fl){
    if(tr==t){
        return fl;
    }
    for(;start[tr]<sz(graf[tr]);start[tr]++){
        int p=graf[tr][start[tr]];
        if(e[p].cap&&level[tr]+1==level[e[p].b]){
            ll ret=dfs(e[p].b,min(fl,e[p].cap));
            if(ret){
                e[p].cap-=ret;
                e[p^1].cap+=ret;
                return ret;
            }
        }
    }
    return 0;
}
ll flow(){
    ll total=0;
    while(bfs()){
        memset(start,0,sizeof start);
        while(ll tr=dfs(s,oo)){
            total+=tr;
        }
    }
    return total;
}


int main(){
    int n,m;
    scanf("%i %i",&n,&m);
    int a,b;
    scanf("%i %i",&a,&b);
    a--;b--;
    addEdge(s,a,oo);
    addEdge(s,b+n,oo);
    addEdge(a+n,t,oo);
    addEdge(b,t,oo);
    for(int i=0;i<m;i++){
        int a,b,l;
        scanf("%i %i %i",&a,&b,&l);
        b--;a--;
        addEdge(a,b+n,l);
        addEdge(a+n,b,l);
        addEdge(b+n,a,l);
        addEdge(b,a+n,l);
    }
    printf("%lld\n",flow());
    bfs();
    for(int i=0;i<n;i++){
        bool a=level[i]!=-1,b=level[i+n]!=-1;
        if(a!=b){
            if(a){
                printf("A");
            }
            else{
                printf("B");
            }
        }
        else{
            printf("C");
        }
    }
    printf("\n");
}