n=gets.to_i
c, v=gets.split.map(&:to_i)

dp=Array.new(2*n){10**9}
dp[0]=dp[1]=0
(1...n).each do |i|
  j=1
  while i+i*j<2*n
    dp[i+i*j]=[dp[i+i*j], dp[i]+c+v*j].min
    j+=1
  end
end

puts dp[n...(2*n)].min