#include<iostream> using namespace std; int main(){ /** char s; int a; cin>>s; a = s; cout<<a; int a; char z; cin>>a; z = a; cout<<z; **/ /** char a,l; cin>>a>>l; cout<<a+l;//字符做加法， 是对应ASCII码相加 char a; int r; cin>>a; r = a; cout<<r; float a; cin>>a; cout<<a*9/5+32; float a,w; cin>>a,w; cout<<a+w;**/ float PI =3.1415926; cout<<PI * 1*1<<endl; cout<<PI * 3*3<<endl; cout<<PI * 5*5<<endl; cout<<PI * 7*7<<endl; cout<<PI * 9*9; return 0; }