public int binarySearch1(){
	int l = 区间左端点, r = 区间右端点;
    while(l<r){
    	int mid = l + r >> 1;
    	if(check(mid)) r = mid;
    	else l = mid + 1;
    }
    return r;
}
public int binarySearch2(){
	int l = 区间左端点, r = 区间右端点;
    while(l<r){
    	int mid = l + r + 1>> 1;
    	if(check(mid)) r = mid - 1;
    	else l = mid;
    }
    return r;
}