from itertools import permutations
from bisect import bisect_left, bisect_right
import random
import math
from collections import deque
from collections import Counter
from collections import defaultdict
inf = 1 << 60


def sgn(x):
    if x > 0:
        return 1
    elif x == 0:
        return 0
    else:
        return -1


def popC(x):
    ans = 0
    while x != 0:
        ans += x % 2
        x //= 2
    return ans


def LI():
    return list(map(int, input().split()))


def II():
    return int(input())


def SI():
    return input()


n = II()
s = list(SI())
x, c = input().split()
x = int(x)
s[x-1] = c
print("".join(s))