delete pics to save space

2.557.cpp

@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <string.h>
+const int N = 50005;
+double p[N];
+void init()
+{
+	p[1]=1;
+	for(int i=1;i<50000;i++)
+		p[i+1]=p[i]*(2*i-1)/(2*i);
+}
+int main()
+{
+	init();
+	int cas,n;
+	scanf("%d", &cas);
+	while(cas--)
+	{
+		scanf("%d",&n);
+		printf("%.4lf\n",1-p[n/2]);
+	}
+	return 0;
+}