UVA 11636 Hello World!

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

int N,ans,cas,x;

int main(){
	cas=1;
	while(scanf("%d",&N)){
		if(N<0)
			break;
		ans=0;x=1;
		while(x<N){
			x*=2;
			ans++;
		}
		printf("Case %d: %d\n",cas++,ans);
	}
	return 0;
}