import sequtils,strutils,math
var
    N = stdin.readline.parseInt
    C,V : int
    ans = 2147483600
(C, V) = stdin.readline.split.map(parseInt)
for i in 1..50000:
    var cos, n, cnt, clip : int
    n = 1
    cnt = 1
    while n < N and cnt <= i:
        cnt += 1
        clip = n
        cos += C
        n += clip
        cos += V
    cos += ceil(max(N - n, 0) / clip).int * V
    ans = min(ans, cos)
echo ans