N = int(input())
C,V = list(map(int, input().split(' ')))

dp = [float('inf') for _ in range(2*N+1)]

minimum = float('inf')
dp[1] = 0
for i in range(1,2*N+1):
    if N <= i:
        minimum = min(minimum, dp[i])
    for j in range(2*i,2*N+1,i):
        dp[j] = min(dp[j], dp[i]+C+(j/i-1)*V)

print(int(minimum))