#include <bits/stdc++.h>
#include <time.h>
#define fi first
#define se second
#define endll "\n"
#define MS0(X) memset((X), 0, sizeof((X)))
#define MS1(X) memset((X), -1, sizeof((X)))
#define LEN(X) strlen(X)
#define max(a,b) (a>b?a:b)
#define min(a,b) (a<b?a:b)
#define rg(a,x,y) (a+x), (a+y+1)
#define vrg(a,x,y) (a.begin()+x),(a.begin()+y+1)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define _sum(a) accumulate(a, 0ll)
#define _max(a,b) *max_element(a,b)
#define pb push_back
#define pr make_pair
#define bugc(_) cerr << (#_) << " = " << (_) << endl;
#define  a(x) a = x;
///vector(len,val);
using namespace std;

typedef long long ll;
typedef double db;
int xx[4] = {1,-1,0,0};
int yy[4] = {0,0,1,-1};
const double eps = 1e-9;
typedef pair<int,int>  P;
typedef pair<ll,ll>  Pl;
typedef pair<double,double>  PP;
const int maxn = 2e6 + 5000;
const ll mod = 1e9 + 7;
const int INF(0x3f3f3f3f);
const ll INFL(0x3f3f3f3f3f3f3f3fll);
inline int sign(db a) { return a < -eps ? -1 : a > eps;}
//inline int cmp(db a,db b){ return sign(a - b);}

ll mul(ll a,ll b,ll c) { ll res = 1; while(b) {  if(b & 1) res *= a,res %= c;  a *= a,a %= c,b >>= 1;  }  return res;}
ll phi(ll x) {  ll res = x;  for(ll i = 2; i * i <= x; i++) { if(x % i == 0) res = res / i * (i - 1);   while(x % i == 0) x /= i;   }  if(x > 1) res = res / x  * (x - 1);    return res;}
template <typename A, typename B> inline bool chmin(A &a, B b){if(a > b) {a = b; return 1;} return 0;}
template <typename A, typename B> inline bool chmax(A &a, B b){if(a < b) {a = b; return 1;} return 0;}
template <typename A, typename B> inline ll add(A x, B y) {if(x + y < 0) return x + y + mod; return x + y >= mod ? x + y - mod : x + y;}
template <typename A, typename B> inline void add2(A &x, B y) {if(x + y < 0) x = x + y + mod; else x = (x + y >= mod ? x + y - mod : x + y);}
template <typename A, typename B> inline ll mul1(A x, B y) {return 1ll * x * y % mod;} /// x * y % mod;
template <typename A, typename B> inline void mul2(A &x, B y) {x = (1ll * x * y % mod + mod) % mod;} /// return x * y
template <typename A> inline void debug(A a){cout << a << '\n';}
template <typename A> inline ll sqr(A x){return 1ll * x * x;}
template <typename A> A inv(A x) {return mul(x, mod - 2);}
template <typename A> void bugl(A a[],int l,int r) { for(int i = l;i <= r;i++) cout << a[i] << " "; cout << endl;  }
template <typename A> void bug(A a[],int l,int r) { for(int i = l;i <= r;i++) cout << a[i] << " "; cout << endl;  }
template<class T>void wt(const T& x){cout << x << endl;}
template<class T>void wt(const T& x, char c){cout << x << c;}
template<class T>void wt(const T& x, const string& s){cout << x << s;}
template<class T>void wt(const T& x, int rnd){
            cout << fixed << setprecision(rnd) << x << endl;}
inline void debug(){  cout << "###!!!" << endl;}
//inline void bugl(int a[],int l,int r){ for(int i = l;i <= r;i++) cout << a[i] << " "; cout << endl; }
//inline void bug(int a[],int l,int r){ for(int i = l;i <= r;i++) cout << a[i] << " ";  }
inline ll read() { char c = getchar(); ll x = 0, f = 1; while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}while(c >= '0' && c <= '9') x = 1ll * x * 10 + c - '0', c = getchar();return x * f;}

int fa[maxn];
int Find(int x) {   if(x != fa[x]) return fa[x] = Find(fa[x]);  return fa[x];}
ll n,k;
ll a[maxn];
int main()
{
    string str;
    while(cin >> n >> k >> str) {
        str[k - 1] += 32;
        cout << str <<endl; 
    }
    return 0;
}














Measured memory_bytes: 2304