delete pics to save space

2.11186.cpp

@@ -0,0 +1,29 @@
+#include<cstdio>
+#include<cmath>
+#include<algorithm>
+using namespace std;
+const double Pi=acos(-1);
+int n,r;
+double res,g[505];
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	while(scanf("%d%d",&n,&r)==2&&n)
+	{
+		for(int i=0;i<n;i++)
+		{
+			scanf("%lf",&g[i]);
+			g[i]=g[i]/180*Pi;
+		}
+		sort(g,g+n);
+		res=0;
+		for(int i=0;i<n;i++)
+			for(int j=i+1;j<n;j++)
+				res+=(n+2*i-2*j)*sin(g[j]-g[i]);
+		res=res*r*r/2;
+		printf("%.0lf\n",res);
+	}
+	return 0;
+}