我帮你改了一下

# include <iostream.h>
# include<math.h>
const double q=acos(-1);
int main()
{
	int t,n;
	float x,y;
	double r;
	cin>>t;
	for(int i=1;i<=t;i++)
	{
		cin>>x>>y;
		r=sqrt(x*x+y*y);
		n=(int)(q*r*r/2)/50;		
		cout<<"Property"<<' ' <<i<<": This property will begin eroding in year "<<n+1<<'.'<<endl;		
	}
		cout<<"END OF OUTPUT."<<endl;
		return 0;
}