#include <stdio.h>

#include <stdlib.h>

#define R 1

#define PI 3.1415


int main() {

float r, s1, s2;

printf("请输入一个数: \n");

scanf("%f", &r);

#if R

s1 = PI * r * r;

printf("圆的的面积为: %f\n", s1);

#else

s2 = r * r;

printf("正方形面积为 %f\n", s2);

#endif

system("pause");

return 0;

}