include

using namespace std;

define FOR(i, a, b) for (int i = (a); i < (b); i++)

define REP(i, n) for (int i = 0; i < (n); i++)

int ripset() { int x; cin>>x; return x; }

const int N = 3000; int a[N];

int main() { int n = ripset(); long ans = 0; REP(i, n) a[i] = ripset(); sort(a, a+n); unordered_map cnt; for (int ii, i = 0; i < n; i = ii) { for (ii = i+1; ii < n && a[i] == a[ii]; ii++); if (ii-i > 1) { int j = 0, k = i-1; long s = 0, h = (ii-i)(ii-i-1)/2; while (j < k) if (a[j]+a[k] < a[i]) j++; else if (a[j]+a[k] > a[i]) k--; else if (a[j] == a[k]) { int t = k-j+1; ans += h(t-1)*t/2*s; ans += h*t*(t-1)(t-2)(t-3)/24; break; } else { int jj = j, kk = k; for (; a[j] == a[jj]; jj++); for (; a[k] == a[kk]; kk--); int f = jj-j, g = k-kk; ans += h*f*g*s; ans += h*f*(f-1)g(g-1)/4; s += f*g; j = jj; k = kk; } } for (int jj, j = ii; j < n; j = jj) { for (jj = j+1; jj < n && a[j] == a[jj]; jj++); if (jj-j > 2) { long h = long(jj-j)(jj-j-1)(jj-j-2)/6; if (3*a[i] == a[j]) ans += long(ii-i)(ii-i-1)(ii-i-2)/6*h; else { int t = a[j]-2*a[i]; auto eq = equal_range(a, a+i, t); if (eq.first != eq.second) ans += long(eq.second-eq.first)(ii-i)(ii-i-1)/2*h; auto it = cnt.find(a[j]-a[i]); if (it != cnt.end()) ans += long(it->second)*(ii-i)h; } } } for (int jj, j = 0; j < i; j = jj) { for (jj = j+1; jj < i && a[j] == a[jj]; jj++); cnt[a[j]+a[i]] += (ii-i)(jj-j); } cnt[2*a[i]] += (ii-i)*(ii-i-1)/2; } cout<