import java.util.*;
class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int K = sc.nextInt();
    String S = sc.next();
    StringBuilder Sb = new StringBuilder();
    Sb.append(S);
    switch (S.charAt(K-1)){
        case 'A': Sb.replace(K-1,K,"a"); break;
        case 'B': Sb.replace(K-1,K,"b"); break;
        case 'C': Sb.replace(K-1,K,"c"); break;
    }
    System.out.println(Sb.toString());
    sc.close();
  }
} import java.util.*; util.* java class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int K = sc.nextInt();
    String S = sc.next();
    StringBuilder Sb = new StringBuilder();
    Sb.append(S);
    switch (S.charAt(K-1)){
        case 'A': Sb.replace(K-1,K,"a"); break;
        case 'B': Sb.replace(K-1,K,"b"); break;
        case 'C': Sb.replace(K-1,K,"c"); break;
    }
    System.out.println(Sb.toString());
    sc.close();
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int K = sc.nextInt();
    String S = sc.next();
    StringBuilder Sb = new StringBuilder();
    Sb.append(S);
    switch (S.charAt(K-1)){
        case 'A': Sb.replace(K-1,K,"a"); break;
        case 'B': Sb.replace(K-1,K,"b"); break;
        case 'C': Sb.replace(K-1,K,"c"); break;
    }
    System.out.println(Sb.toString());
    sc.close();
  } main {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int K = sc.nextInt();
    String S = sc.next();
    StringBuilder Sb = new StringBuilder();
    Sb.append(S);
    switch (S.charAt(K-1)){
        case 'A': Sb.replace(K-1,K,"a"); break;
        case 'B': Sb.replace(K-1,K,"b"); break;
        case 'C': Sb.replace(K-1,K,"c"); break;
    }
    System.out.println(Sb.toString());
    sc.close();
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int K = sc.nextInt(); K sc.nextInt() sc.nextInt sc String S = sc.next(); S sc.next() sc.next sc StringBuilder Sb = new StringBuilder(); Sb new StringBuilder() Sb.append(S) Sb.append Sb S switch (S.charAt(K-1)){
        case 'A': Sb.replace(K-1,K,"a"); break;
        case 'B': Sb.replace(K-1,K,"b"); break;
        case 'C': Sb.replace(K-1,K,"c"); break;
    } S.charAt(K-1) S.charAt S K-1 K 1 case 'A': 'A' case 'A': Sb.replace(K-1,K,"a") Sb.replace Sb K-1 K 1 K "a" break; case 'B': 'B' case 'B': Sb.replace(K-1,K,"b") Sb.replace Sb K-1 K 1 K "b" break; case 'C': 'C' case 'C': Sb.replace(K-1,K,"c") Sb.replace Sb K-1 K 1 K "c" break; System.out.println(Sb.toString()) System.out.println System.out System System.out Sb.toString() Sb.toString Sb sc.close() sc.close sc String[] args args
import java.util.*;
class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int K = sc.nextInt();
    String S = sc.next();
    StringBuilder Sb = new StringBuilder();
    Sb.append(S);
    switch (S.charAt(K-1)){
        case 'A': Sb.replace(K-1,K,"a"); break;
        case 'B': Sb.replace(K-1,K,"b"); break;
        case 'C': Sb.replace(K-1,K,"c"); break;
    }
    System.out.println(Sb.toString());
    sc.close();
  }
}