问题分析：

1. 每个王国是平面上的凸包
2. 导弹击中凸包内部则摧毁发电厂
3. 需要计算被摧毁王国的总面积

关键点：

• 凸包计算
• 点是否在多边形内的判断
• 面积累加

解题步骤：

1. 对每个王国计算凸包
2. 检查每个导弹是否在凸包内
3. 标记被击中的王国
4. 计算被标记王国的总面积

#include <cstring>
#include <algorithm>
using namespace std;
int const MAX = 105;
int n;
struct POINT {
    int x, y;
}base, p[MAX];
 
struct AREA {
    int top;
    double area;
    POINT stk[MAX];
}a[25];
bool vis[25];
 
void getBase() {  
    scanf("%d %d", &p[0].x, &p[0].y);  
    base.x = p[0].x;  
    base.y = p[0].y;  
    int pos = 0;  
    for (int i = 1; i < n; i ++) {  
        scanf("%d %d", &p[i].x, &p[i].y);  
        if (p[i].y < base.y || (p[i].y == base.y && p[i].x < base.x)) {  
            base.x = p[i].x;  
            base.y = p[i].y;  
            pos = i;  
        }  
    }  
    swap(p[0], p[pos]);  
}  
 
int getDist(POINT p1, POINT p2) {
    return (p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y);
}
 
int getCross(POINT p0, POINT p1, POINT p2) {
    return (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y);
}
 
bool cmp(POINT p1, POINT p2) {
    if (getCross(base, p1, p2) == 0) {
        return getDist(base, p1) < getDist(base, p2);
    }
    if (getCross(base, p1, p2) > 0) {
        return true;
    }
    return false;
}
 
void getConvex(int i) {
    sort(p + 1, p + n, cmp);
    a[i].stk[0] = p[0];
    a[i].stk[1] = p[1];
    a[i].top = 1;
    for (int j = 2; j < n; j ++) {
        while (a[i].top > 0 && getCross(a[i].stk[a[i].top - 1], a[i].stk[a[i].top], p[j]) <= 0) {
            a[i].top --;
        }
        a[i].stk[++ a[i].top] = p[j];
    }
}
 
void getArea(int i) {
    a[i].stk[++ a[i].top] = p[0];
    for (int j = 0; j < a[i].top; j ++) {
        a[i].area += getCross(base, a[i].stk[j], a[i].stk[j + 1]);
    }
    a[i].area /= 2.0;
}
 
int main() {
    int cnt = 0;
    while(scanf("%d", &n) && n != -1) {
        getBase();
        getConvex(cnt);
        getArea(cnt);
        cnt ++;
    }
    POINT t;
    double ans = 0;
    while(scanf("%d %d", &t.x, &t.y) != EOF) {
        bool flag = false;
        for (int i = 0; i < cnt && !flag; i ++) {
            if (!vis[i]) {
                for (int j = 0; j < a[i].top && !flag; j ++) {
                    if (getCross(a[i].stk[0], a[i].stk[j], t) >= 0 &&  getCross(a[i].stk[0], a[i].stk[j + 1], t) <= 0) {
                        if (getCross(a[i].stk[j], t, a[i].stk[j + 1]) <= 0) {
                            vis[i] = true;
                            flag = true;
                            ans += a[i].area;
                        }
                    }
                } 
            }
        }
    } 
    printf("%.2f\n", ans);
}