#include <iostream>
#include <utility>
#include <string>

std::pair<bool, int> lang1(std::string& s, int i) {
    int idx = i, last = i;
    while (s[idx] == 'a' or s[idx] == 'b') {
        if (s[idx] == 'a') last = idx;
        idx++;
    }
    if (last != i) {
        return { true, last + 1 };
    } else {
        return { false, i };
    }
}

std::pair<bool, int> lang2(std::string& s, int i) {
    int idx = i, tam = s.size( );
    while ((s[idx] == 'x' and s[idx + 1] == 'y') or (s[idx] == 'x' and s[idx + 1] == 'z')) {
        idx += 2;
    }
    return { true, idx };
}

std::pair<bool, int> lang3(std::string& s, int i) {
    int idx = i;
    while (std::isspace(s[idx])) idx++;
    return { true, idx };
}

int main( ) {
    std::string cad;
    std::getline(std::cin, cad, '!');
    for (int i = 0; i < cad.size( ); ++i) {
        if (cad[i] == 'a') {
            std::pair<bool, int> res = lang1(cad, i);
            if (res.first) {
                std::cout << "L1\n";
                i += (res.second - i - 1);
            } else {
                std::cout << "ERROR\n";
            }
        } else if ((cad[i] == 'x' and cad[i + 1] == 'y') or (cad[i] == 'x' and cad[i + 1] == 'z')) {
            std::pair<bool, int> res = lang2(cad, i);
            if (res.first) {
                std::cout << "L2\n";
                i += (res.second - i - 1);
            } else {
                std::cout << "ERROR\n";
            }
        } else if (std::isspace(cad[i])) {
            std::pair<bool, int> res = lang3(cad, i);
            if (res.first) {
                std::cout << "BLANK\n";
                i += (res.second - i - 1);
            }
        } else {
            std::cout << "ERROR\n";
        }
    }
}