#include <cstring>#include <cstdio>#include <cstdlib>#include <algorithm>#include <iostream>using namespace std;int N, L, T[2050];char pre[2050][1050];int main() { int ret, lim; while (scanf("%d %d", &N, &L), N|L) { ret = 0; lim = N << 1; for (int i = N; i < lim; i++) { scanf("%s", pre[i]); } for (int p = 0; p < L; ++p) { for (int i = N; i < lim; ++i) { T[i] = 1 << (pre[i][p]-'A'); } for (int i = N-1; i > 0; --i) { int lch = i << 1, rch = i << 1 | 1; T[i] = T[lch] & T[rch]; if (T[i] == 0) { T[i] = T[lch] | T[rch]; ++ret; } } for (int i = 0; i < 26; ++i) { if (T[1] & (1 << i)) { putchar('A' + i); break; } } } printf(" %dn", ret); } return 0;}
