Wrong Answer

JOI2010_4.cpp

#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
class M {
public:
	int total, pos;
	M(int total, int pos){
		this->total = total;
		this->pos = pos;
		return;
	}
};
int main()
{
	int N;
	scanf("%d\n", &N);
	vector<int> v(N);
	for(int i = 0; i < N; i++)
		scanf("%d", &v[i]);
	v.pop_back();
	N--;
	long long total = 0;
	queue<M> q;
	q.push(M(v[0], 1));

	while(!q.empty()){
		M m = q.front(); q.pop();

		if(m.pos > (N - 1)){
			total++;
			continue;
		}
		int t = m.total + v[m.pos];
		if(0 <= t && t < 20){
			q.push(M(t, m.pos + 1));
		}
		t = m.total - v[m.pos];
		if(0 <= t && t < 20){
			q.push(M(t, m.pos + 1));
		}
	}
	printf("%lld\n", total);
	return 0;
}