HDU 5174

#include <cstdio> 
#include <iostream> 
#include <cstring>  
#include <cctype>  
#include <algorithm>  
#define LL __int64
using namespace std; 
const LL MAX=2147483647;
const int N=110;
LL friends[N];
int n;LL tot;
struct Node{
	LL v,c;
}node[N];
bool cmp(LL a,LL b){
	if(a<b) return true;
	return false;
}
int main(){
	int t=0;
	while(scanf("%d",&n)!=EOF){
		tot=-1;
		for(int i=0;i<n;i++){
			scanf("%I64d",&friends[i]);
			node[i].c=0;
		}
		sort(friends,friends+n,cmp);
		for(int i=0;i<n;i++){
			if(i==0||friends[i]!=friends[i-1]){
				node[++tot].v=friends[i];
				node[tot].c++;
			}
			else if(friends[i]==friends[i-1])
			node[tot].c++;
		}
		if(tot==0){
			printf("Case #%d: -1\n",++t);
			continue;
		}
		LL now,le,rig; tot++;
		LL ans=0;
		for(LL i=0;i<tot;i++){
			now=i;
			le=((i-1)%tot+tot)%tot,rig=((i+1)%tot+tot)%tot;
			if((node[now].v+node[le].v)%MAX==node[rig].v)
			ans+=node[now].c;
		}
		printf("Case #%d: %I64d\n",++t,ans);
	}
	return 0;
}