def mutate_string(string, position, character):
    
    # Slice the string and join it back (quicker but harder to visualize)
    '''
The string is sliced into two parts:
string[:position]: from the start of the string up to (but not including) the position index.
string[position+1:]: from the character right after the position index until the end of the string.

We process to put the character between the parts
    '''
    s_new = string[:position] + character + string[position+1:]
    
    return s_new

if __name__ == '__main__':
    s = input()
    i, c = input().split()
    s_new = mutate_string(s, int(i), c)
    print(s_new)