local S_dash=io.read()
local T=io.read()

local flag=true
for i=1,#S_dash-#T+1 do
    local subS=S_dash:sub(i,#T+i-1)
    for j=1,#T do
        if subS:sub(j,j)~="?" and subS:sub(j,j)~=T:sub(j,j) then
            flag=false
        elseif subS:sub(j,j)==T:sub(j,j) then
            flag=true
        end
    end
    if flag then
        S_dash=S_dash:sub(1,i-1)..T..S_dash:sub(#T+i)
    end
end
S=S_dash:gsub("%?","a")
print(flag and S or "UNRESTORABLE")