// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
using namespace std;
#define MAXN 500010
#define MOD 1000000007
typedef long long ll;
typedef pair<ll, ll> pi;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int tt; tt = 1;
	while (tt--) {
		int n; cin >> n;
		vector<int> a(n+1);
		for (int i = 1; i <= n; i++) cin >> a[i];
		ll idx = 2000;
		vector<ll> dp[n+1], cnt[n+1];
		vector<int> last(25, 0);
		dp[0].resize(idx+10, 0);
		cnt[0].resize(idx+10, 0);
		dp[0][1000] = 1;
		for (int i = 1; i <= n; i++) {
			dp[i].resize(idx+10, 0);
			cnt[i].resize(idx+10, 0);
			for (int j = 0; j <= idx; j++) dp[i][j] = dp[i-1][j];
			for (int j = 0; j <= idx; j++) cnt[i][j] = cnt[i-1][j];
			for (int j = 10; j <= idx-10; j++) {
				if (j == 1000) {
					if (last[a[i] + 10] == 0) cnt[i][j + a[i]] = (cnt[i][j + a[i]] % MOD + dp[i-1][j] % MOD) % MOD;
					else cnt[i][j + a[i]] = ((cnt[i][j + a[i]] + dp[i-1][j] - dp[last[a[i] + 10]-1][j]) + MOD) % MOD;
				} else dp[i][j + a[i]] = ((dp[i][j + a[i]] + dp[i-1][j]) % MOD + cnt[i-1][j]) % MOD;
			}
			last[a[i] + 10] = i;
		}
		ll ans = 0;
		for (int i = 0; i <= idx; i++) ans = (ans + dp[n][i]) % MOD;
		cout << ans << "\n";
	}
}