#!/usr/bin/env python3.8
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
from functools import lru_cache

# %%
N, C, V = map(int, read().split())


# %%
@lru_cache(None)
def f(N):
    # N倍するためのコスト
    if N == 1:
        return 0
    sqN = int(N ** .5)
    ret = 10 ** 9
    for i in range(2, N + 1):
        j = (N+i-1) // i
        if j <= sqN:
            break
        x = C + (i - 1) * V + f(j)
        if ret > x:
            ret = x
    for j in range(1, sqN + 1):
        i = (N + j - 1) // j
        x = C + (i - 1) * V + f(j)
        if ret > x:
            ret = x
    return ret


# %%
print(f(N))