# include <stdio.h>int main () int sum;? ? int a; double pai=3.14;printf("請輸入a的值");scanf("%d",&a);{ ? ?void action1(int),action2(int,int),action3(int); int bianhao;? ? scanf("%d",&bianhao); printf("請選擇編號：1，正方形；2，長方形；3，圓形；"); switch(bianhao) { case '1':action1(a);break; case '2':action2(a);break; case '3':action3(a);break; default:printf("enter datd error"); } return 0;}void action1(int x){ printf("sum=a*a%d\n",sum);}void action2(int x,int y){ printf("sum=x*y%d\n",sum);}void action3 (int r){ printf("sum=pai*r*r%d\n",sum);}