#include<bits/stdc++.h>
#define endl '\n'
#define F first
#define S second
// #define int ll
#define rep(i, s, e) for(int i = s, i##E = e; i <= i##E; ++i)
#define per(i, s, e) for(int i = s, i##E = e; i >= i##E; --i)
#define gmin(x, y) (x = min(x, y))
#define gmax(x, y) (x = max(x, y))
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double f128;
typedef pair<int, int> pii;
#ifndef ONINE_JUDGE
#define debug(fmt, ...) fprintf(stderr, "[%d] " fmt "\n", __LINE__, ##__VA_ARGS__)
#else
#define debug(fmt, ...) 0
#endif

char gc() {
    static char buf[1 << 20], *st, *ed;
    if(st == ed) st = buf, ed = buf + fread(buf, 1, 1 << 20, stdin);
    return st == ed ? EOF : *st++;
}
template<typename Int>
bool read(Int &x) {
    int flg = 1, c = EOF;
    while(!isdigit(c = gc()) && c != '-' && c != EOF);
    if(c == EOF) return 0;
    if(c == '-') flg = -1, x = 0;
    else x = c - '0';
    while(isdigit(c = gc())) x = x * 10 + c - '0';
    x *= flg;
    return 1;
}
template<typename Int, typename ...Args>
bool read(Int &x, Args& ...args) {
    if(!read(x)) return 0;
    return read(args...);
}

constexpr int N = 2005;
int n, p, m, fa[N], sz[N], id[N], tot;
char s[N][N];
bitset<N> to[N];

int Log(int x) {
    if(x == 1) return 1;
    int t = __lg(x);
    return (1 << t) == x ? t : t + 1;
}

void slove() {
    // debug("%d %d %d", n, p, m);
    rep(i, 1, p) {
        int u, v; read(u, v);
        to[u][v] = to[v][u] = 1;
    }
    int l = 0, r = 0, lmx = 1, rmx = 1;
    rep(i, 1, n) {
        bool flg = 1;
        per(j, i - 1, 1) if(to[i] == to[j]) {
            fa[i] = j, id[i] = id[j] + 1, sz[i] = sz[j] + 1;
            gmax(lmx, sz[i]);
            flg = 0; break;
        }
        if(flg) ++l, fa[i] = i, sz[i] = 1;
    }
    rep(i, n + 1, n * 2) {
        bool flg = 1;
        per(j, i - 1, n + 1) if(to[i] == to[j]) {
            fa[i] = j, id[i] = id[j] + 1, sz[i] = sz[j] + 1;
            gmax(rmx, sz[i]);
            flg = 0; break;
        }
        if(flg) ++r, fa[i] = i, sz[i] = 1;
    }
    // rep(i, 1, n * 2) debug("%d %d", id[i], sz[i]);
    debug("%d %d %d %d", l, r, lmx, rmx);
    if(l < r) {
        rep(i, 1, n) {
            if(fa[i] != i) continue;
            s[i][++tot] = 'B';
            rep(j, 1, n) if(j != i) s[j][tot] = 'A';
            rep(j, n + 1, n * 2) 
                s[j][tot] = to[i][j] ? 'B' : 'C';
        }
        rep(x, 1, Log(lmx)) {
            ++tot;
            rep(i, 1, n) s[i][tot] = id[i] >> (x - 1) & 1 ? 'C' : 'A';
            rep(i, n + 1, n * 2) s[i][tot] = 'B';
        }
        if(rmx || lmx) rep(x, 1, Log(rmx)) {
            ++tot;
            rep(i, n + 1, n * 2) s[i][tot] = id[i] >> (x - 1) & 1 ? 'C' : 'B';
            rep(i, 1, n) s[i][tot] = 'A';
        }
    }
    else {
        rep(i, n + 1, n * 2) {
            if(fa[i] != i) continue;
            s[i][++tot] = 'B';
            rep(j, n + 1, n * 2) if(j != i) s[j][tot] = 'A';
            rep(j, 1, n) s[j][tot] = to[i][j] ? 'B' : 'C';
        }
        rep(x, 1, Log(rmx)) {
            ++tot;
            rep(i, n + 1, n * 2) s[i][tot] = id[i] >> (x - 1) & 1 ? 'C' : 'A';
            rep(i, 1, n) s[i][tot] = 'B';
        }
        if(rmx || lmx) rep(x, 1, Log(lmx)) {
            ++tot;
            rep(i, 1, n) s[i][tot] = id[i] >> (x - 1) & 1 ? 'C' : 'B';
            rep(i, n + 1, n * 2) s[i][tot] = 'A';
        }
    }
    printf("%d\n", tot);
    rep(i, 1, n * 2) puts(s[i] + 1);

    rep(i, 1, n * 2) to[i].reset();
    rep(i, 1, n * 2) fa[i] = id[i] = sz[i] = 0;
    rep(i, 1, n * 2) rep(j, 1, tot) s[i][j] = 0;
    tot = 0;
}

signed main() {
    while(read(n, p, m)) slove();
    return 0;
}