c语言结构体 求矩形的面积 编译通过不了 想知道怎么改

#include<stdio.h>
struct point{
    int x;
    int y;    
}upper_left,lower_right;
struct rectangle{
    struct point.upper_left,struct point.lower_right;
};
int main(){
    int s,a,b;
    a=rectangle.lower_right.x-rectangle.upper_left.x;
    b=rectangle.upper_left.y-rectangle.lower_right.y;
    s=a*b;
    printf("r的面积是%d",s);
    return 0;
}

 
#include<stdio.h>
struct point{
    int x;
    int y;    
};
struct rectangle{
    struct point upper_left;
    struct point lower_right;
};
int main(){
    int s,a,b;
    struct rectangle c, d;
    a=c.lower_right.x-c.upper_left.x;
    b=d.upper_left.y-d.lower_right.y;
    s=a*b;
    printf("r的面积是%d",s);
    return 0;
}

struct Rectangle定义不对。

struct rectangle{
    struct point.upper_left,struct point.lower_right;
};
改为
struct rectangle{
    struct point p1;
    struct point p2;
};