https://old.ynoip.cn/p/1112

#include <cstdio>
#include <cmath>
using namespace std;

int main(void) {
	double weight;
	scanf("%lf", &weight);
	weight = ceill(weight);
	if (weight <= 20.0)
		printf("%.2lf", weight * 1.68);
	else
		printf("%.2lf", 20.0 * 1.68 + (weight - 20.0) * 1.98);
	return 0;
}