>>7
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
struct point_t{double x;double y;};
int main(void){char tmp[100];struct point_t pt[2];int i;for(i=0;i<2;i++){
printf("x(%d)=",i);fgets(tmp,sizeof(tmp),stdin);pt[i].x=atof(tmp);
printf("y(%d)=",i);fgets(tmp,sizeof(tmp),stdin);pt[i].y=atof(tmp);}
printf("%lf\n",abs(pt[1].x-pt[0].x)*abs(pt[1].y-pt[0].y));return 0;}