喝汽水问题:1瓶汽水1元，2个空瓶可以换一瓶汽水，给20元，可以喝多少汽水

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{   
	int n = 20;
	int sum = 20;
	int empty = 20;
	while (empty > 1)
	{
		sum += empty / 2;
		empty = empty / 2 + empty % 2;
	}
	printf("%d", sum);
	return 0;
}