//服务端第三题，ac

#include<iostream>
#include<string>
#include<vector>
using namespace std;

void getResult(string& temp, vector<string>& r, string& tempIn, int p) {
    if (p >= temp.size()) {
        r.push_back(tempIn);
        return;
    }
    tempIn.push_back(temp[p] - '0' - 1+ 'a');
    getResult(temp, r, tempIn, p + 1);
    tempIn.pop_back();
    if (temp.size()-p <= 1)return;
    if (temp[p] <= '2'&&temp[p + 1] <= '6' || temp[p] <= '1') {
        tempIn.push_back(((temp[p] - '0') * 10 + (temp[p + 1] - '0')) - 1 + 'a');
        getResult(temp, r, tempIn,p + 2);
        tempIn.pop_back();
    }
}

int main(void) {
    string temp, r, tempIn;
    vector<string> result;  
    while (cin >> temp) {
        getResult(temp, result, tempIn, 0);
        for (int i = 0; i < result.size(); ++i) { 
            for(int j=0;j<result[i].size();++j)
                printf("%c",result[i][j]); 
            if (i == result.size() - 1)printf("\n");
            else  printf(" ");
        }
        r.clear();
        tempIn.clear();
        result.clear();
        temp.clear();
    }
    return 0;
}