#include<iostream>
using std::cin;
using std::cout;
using std::endl;
int main()
{
cout<<"請選擇妳要計算的圖形:"<<endl;
cout<<"A.圓形B.正方形C.矩形"<<endl;
char s;cin>>s;double a,b;
switch(s)
{
case 'a':
cout<<"請輸入半徑:"<<endl;
cin>>a;
cout<<"園的面積為:"<<3.14*a*a<<endl;
break;
case 'b':
cout<<"請輸入正方形邊長:"<<endl;
cin>>a;
cout<<"正方形面積為:"<<a*a<<endl;
break;
case 'c':
cout<<"請輸入長方形的長"<<endl;
cin>>a;
cout<<"請輸入長方形的寬"<<endl;
cin>>b;
cout<<"長方形的面積為:"<<a*b<<endl;
break;
default:
cout<<"輸入錯誤!"<<endl;
}
return 0;
}