import sys
readline=sys.stdin.readline

N=int(readline())
inf=1<<30
dp=[inf]*(N+1)
dp[1]=0
C,V=map(int,readline().split())
for i in range(1,N+1):
    for j in range(i,N+i+1,i):
        dp[min(j,N)]=min(dp[min(j,N)],dp[i]+C+V*(j//i-1))
ans=dp[N]
print(ans)