#include <stdio.h>
#include <math.h>
int main()
{
	float f,x;
	printf("请输入一个数\n");
	scanf("%f",&x);
	
	switch ((int)(x/1)) {
	case 0:
		f=0;
		break;
	case 1:
		f=3*x+5;
		break;
	case 2:
		f=3*sin(x)-1;
		break;
	case 3:
		f=log(1+x*x);
		break;
		
	case 4:
		f=log10(x*x-2*x)+5;
		break;
	default:
		f=-1;
		break;
	}
	printf("输入:%f,结果:%f",x,f);
}

#include <stdio.h>
int main()
{
	float g,n;
	float m=0;
	printf("请输入重量\n");
	scanf("%f",&g);
	if(g>50) {
		printf("拒收");
		return 0;
	}
	n=g;
	switch ((int)g/5) {
		case 10:
		case 9:
		case 8:
		case 7:
		case 6:
			m+=5.0*(g-30);
			g=30;
		case 5:
		case 4:
			m+=4.5*(g-20);
			g=20;
		case 3:
		case 2:
			m+=4.0*(g-10);
			g=10;
		case 1:
			m+=3.5*(g-5);
			g=5;
		case 0:
			m+=3.0*g;
			break;
		default:
			m=-1;
			break;
	}
	
	printf("重量:%.2fkg,快递费:%.2f",n,m);
}