n,c,v;
a,b,t;
ans=1e9;
main(){
	scanf("%d%d%d",&n,&c,&v);
	for(int k=1;k<log2(n)+1;k++){
		a=pow(n,1.0/k);
		b=(log(n)-k*log(a))/(log(a+1)-log(a))+1;
		t=(c-v)*k+v*(a*k+b);
		ans=fmin(ans,t);
	}
	printf("%d",ans);
}