///Thue Morse
#include <bits/stdc++.h>
using namespace std;

char cond_commute_case(const char ch, const int n){
    return ch ^ (n * ('a' ^ 'A')); }

char resolve(const int n, const int q, const string& str){
    return cond_commute_case(str[q%n], __builtin_popcount(q/n)%2); }

int main(){
    int n, k, q;
    string str;
    cin >> n >> k >> str >> q;
    const char critical_char = resolve(n, q, str);
cout<<critical_char;

    return 0;
}