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#include <bits/stdc++.h>

using namespace std;

typedef unsigned uint;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ldbl;
typedef pair<int, int> pii;
typedef pair<uint, uint> puu;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<double, double> pdd;
typedef vector<int> vi;
typedef vector<uint> vu;
typedef vector<ll> vll;
typedef vector<ull> vull;
typedef vector<pii> vpii;
typedef vector<puu> vpuu;
typedef vector<pll> vpll;
typedef vector<pull> vpull;
typedef vector<string> vstr;
typedef vector<double> vdbl;
typedef vector<ldbl> vldbl;
#define pb push_back
#define ppb pop_back
#define pfr push_front
#define ppfr pop_front
#define emp emplace
#define empb emplace_back
#define be begin
#define rbe rbegin
#define all(x) (x).be(), (x).end()
#define rall(x) (x).rbe(), (x).rend()
#define fir first
#define sec second
#define mkp make_pair
#define brif(cond) if (cond) break
#define ctif(cond) if (cond) continue
#define retif(cond) if (cond) return
void canhazfast() {ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);}
template<typename T> T gcd(T a, T b) {return b ? gcd(b, a%b) : a;}
template<typename T> T extgcd(T a, T b, T &x, T &y)
{
    T x0 = 1, y0 = 0, x1 = 0, y1 = 1;
    while (b) {
        T q = a/b; a %= b; swap(a, b);
        x0 -= q*x1; swap(x0, x1);
        y0 -= q*y1; swap(y0, y1);
    }
    x = x0; y = y0; return a;
}
int ctz(uint x) {return __builtin_ctz(x);}
int ctzll(ull x) {return __builtin_ctzll(x);}
int clz(uint x) {return __builtin_clz(x);}
int clzll(ull x) {return __builtin_clzll(x);}
int popcnt(uint x) {return __builtin_popcount(x);}
int popcntll(ull x) {return __builtin_popcountll(x);}
int bsr(uint x) {return 31^clz(x);}
int bsrll(ull x) {return 63^clzll(x);}

#define N 100032
#define LLINF ((ll)5e14)

char dir[N];
int a[N], b[N], x[N], d[N];
ll psum[N], pre_min[N], suf_max[N], dp[N];
vpii path[N];

ll calc(int n)
{
    ll cur = 0, res = 0;
    for (int i = 0; i < n; ++i) {
        cur = max(cur+x[i], 0LL);
        res = max(res, cur);
    }
    return res;
}

int main()
{
    canhazfast();

    int n, k;
    int ma, mb, m;
    ll lo, hi = LLINF;
    vi va, vb, v0, bad;

    cin >> n >> k;
    for (int i = 0; i < n; ++i) cin >> a[i];
    for (int i = 0; i < n; ++i) cin >> b[i];

    for (int i = 0; i < n; ++i) {
        x[i] = min(a[i], b[i]);
        d[i] = abs(a[i]-b[i]);
        if (a[i] < b[i]) {
            va.pb(i);
            dir[i] = 'A';
        } else if (a[i] > b[i]) {
            vb.pb(i);
            dir[i] = 'B';
        } else {
            v0.pb(i);
        }
    }
    ma = (int)va.size();
    mb = (int)vb.size();

    lo = calc(n); /// no flips
    if (k >= ma && k <= n-mb) {
        for (int i = ma; i < k; ++i) dir[v0[i-ma]] = 'A';
        for (int i = k; i < n-mb; ++i) dir[v0[i-ma]] = 'B';
        cout << lo << '\n' << dir << '\n';
        return 0;
    }

    for (int i = 0; i < n; ++i) {
        psum[i+1] = psum[i]+x[i];
        pre_min[i+1] = min(pre_min[i], psum[i+1]);
    }
    suf_max[n] = psum[n];
    for (int i = n-1; i >= 0; --i) suf_max[i] = max(suf_max[i+1], psum[i]);

    if (k < ma) {
        /// A -> B
        swap(bad, va);
        for (int i : v0) dir[i] = 'B';
        m = ma;
        k = ma-k;
    } else {
        /// B -> A
        swap(bad, vb);
        for (int i : v0) dir[i] = 'A';
        m = mb;
        k = k-n+mb;
    }

    /// init UB
    /// flip first k
    for (int i = 0; i < k; ++i) x[bad[i]] += d[bad[i]];
    hi = calc(n);
    /**
    /// k smallest
    auto cmp = [](int x, int y) -> bool {
        return d[x] < d[y];
    };
    v0 = bad;
    sort(all(v0), cmp);
    for (int i = 0; i < k; ++i) {
        int u = v0[i];
        x[u] += d[u];
    }
    hi = calc(n);
    /// random
    for (int c = 0; c < 20; ++c) {
        random_shuffle(all(v0));
        for (int i = 0; i < k; ++i) {
            int u = v0[i];
            x[u] += d[u];
        }
        hi = min(hi, calc(n));
        for (int i = 0; i < k; ++i) {
            int u = v0[i];
            x[u] -= d[u];
        }
    }**/

    /// optimize
    while (lo < hi) {
        ll v = (lo+hi)/2;
        int kmax = 0;
        dp[0] = 0;
        for (int i = 0; i < m; ++i) {
            int min_pos = max(k-m+i, 0);
            brif(min_pos > kmax);
            int u = bad[i];
            ll pref = -pre_min[u];
            ll limit = v-d[u]-suf_max[u+1];
            ctif(pref > limit);
            int pos = upper_bound(dp, dp+kmax+1, limit)-dp-1;
            if (pos == kmax) {
                dp[++kmax] = max(dp[pos], pref)+d[u];
                brif(kmax == k);
                --pos;
            }
            for (int j = pos; j >= min_pos; --j) {
                ll g = max(dp[j], pref)+d[u];
                dp[j+1] = min(dp[j+1], g);
                brif(dp[j] <= pref+d[u]);
            }
        }
        if (kmax == k) hi = v;
        else lo = v+1;
    }

    /// reconstruct
    {
        ll v = lo;
        int kmax = 0;
        dp[0] = 0;
        path[0].empb(-1, -1);
        for (int i = 0; i < m; ++i) {
            int min_pos = max(k-m+i, 0);
            ///brif(min_pos > kmax);
            int u = bad[i];
            ll pref = -pre_min[u];
            ll limit = v-d[u]-suf_max[u+1];
            ctif(pref > limit);
            int pos = upper_bound(dp, dp+kmax+1, limit)-dp-1;
            if (pos == kmax) {
                dp[++kmax] = max(dp[pos], pref)+d[u];
                path[kmax].empb(u, path[pos].back().fir);
                brif(kmax == k);
                --pos;
            }
            for (int j = pos; j >= min_pos; --j) {
                ll g = max(dp[j], pref)+d[u];
                if (dp[j+1] > g) {
                    dp[j+1] = g;
                    path[j+1].empb(u, path[j].back().fir);
                }
                brif(dp[j] <= pref+d[u]);
            }
        }
        for (int i = k; i > 0; --i) {
            int u, p;
            tie(u, p) = path[i].back();
            dir[u] ^= 'A'^'B';
            while (path[i-1].back().fir != p) path[i-1].ppb();
        }
    }

    /// print
    cout << lo << '\n';
    cout << dir << '\n';

    return 0;
}