> using namespace std;
> #include <iostream>
> #include <iomanip>
> #include <algorithm>
> #include <cstdio>
> #include <cmath>
> #include <complex>
> 
> //这道题pi后面加多少位都没关系
> double pi = 3.141592653589793238462643383279502884197;
> 
> typedef complex<double> CX;
> double circle_inter(CX o1, double r1, CX o2, double r2){
> 	double d = sqrt( norm(o1-o2) );
> 	if( d >= r1 + r2 ) return 0;
> 	if( d <= abs(r1 - r2) ) return min(pi * r1 * r1, pi * r2 * r2 );
> 	double t1 = acos(( d*d + r1*r1 - r2*r2 ) / 2 / d / r1);
> 	double t2 = acos(( d*d + r2*r2 - r1*r1 ) / 2 / d / r2);
> 	double area = pi * r1 * r1 + pi * r2 * r2;
> 	area -= t1 * r1 * r1;
> 	area -= t2 * r2 * r2;
> 	double s = ( r1 + r2 + d )/2;
> 	area += sqrt( s * (s - r1 ) * (s - r2 ) * (s - d)) * 2;
> 	return pi*r1*r1 + pi*r2*r2 - area;
> }
> 
> int main() {
> 	double x1, y1, x2, y2, r1, r2;
> 	while(cin >> x1 >> y1 >> r1 >> x2 >> y2 >> r2){
> 		double area = circle_inter( CX(x1,y1), r1, CX(x2, y2), r2);
> 
> // 使用这句就会WA
> //	   	printf("%.3lf\n", circle_inter( CX(x1,y1), r1, CX(x2, y2), r2));
> 
> // 这句就AC了
> 		cout<<setiosflags(ios::fixed)<<setprecision(3)<<area<<endl;
> 	}
> 	return 0;
> }
printf(".f")not .lf