local function str2tbl(s)
    local t = {string.byte(s, 1, #s)}
    for i=1, #t do
        t[i] = string.char(t[i])
    end
    return t
end

local function str2numtbl(s, offset)
    local t = {string.byte(s, 1, #s)}
    if offset then
        for i=1, #t do
            t[i] = t[i] - offset
        end
    end
    return t
end

--local function each_char2(s)
--    return ipairs(str2tbl(s))
--end

local function each_char(s)
    local f = function(_, i)
        i = i + 1
        if i <= #s then
            return i, string.sub(s, i, i)
        end
    end
    return f, nil, 0
end

function string.at(s, i)
    return string.sub(s, i, i)
end

--
local N,_,S,K = io.read("n", "l", "l", "n")
local c = S:at(K)
local ans = string.gsub(S, "[^"..c.."]", "*")
print(ans)