#pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #include using namespace std; typedef long long ll; typedef long double ld; #define REP(i, n) for (int i = 0; i < (n); ++i) #define REPR(i, n) for (int i = n - 1; i >= 0; --i) #define FOR(i, m, n) for (int i = m; i < n; ++i) #define FORR(i, m, n) for (int i = m; i >= n; --i) #define ALL(v) (v).begin(),(v).end() #define ALLR(v) (v).rbegin(),(v).rend() #define SORT(v) sort(ALL(v)) #define RSORT(v) sort(ALLR(v)) #define REV(v) reverse(ALL(v)) #define UNIQUE(x) SORT(x), x.erase(unique(ALL(x)), x.end()) #define fi first #define se second #define PB push_back #define EB emplace_back using pii = pair; using pll = pair; template using vc = vector; template using vvc = vector>; template using vvvc = vector>; using vi = vc; using vl = vc; using vpi = vc; using vpl = vc; // noimi #define INT(...) int __VA_ARGS__;IN(__VA_ARGS__) #define LL(...) ll __VA_ARGS__;IN(__VA_ARGS__) #define STR(...) string __VA_ARGS__;IN(__VA_ARGS__) #define DBL(...) double __VA_ARGS__;IN(__VA_ARGS__) #define VEC(type, name, size) vector name(size);IN(name) #define VEC2(type, name1, name2, size) vector name1(size), name2(size);for(int i = 0; i < size; i++) IN(name1[i], name2[i]) #define VEC3(type, name1, name2, name3, size) vector name1(size), name2(size), name3(size);for(int i = 0; i < size; i++) IN(name1[i], name2[i], name3[i]) #define VEC4(type, name1, name2, name3, name4, size) vector name1(size), name2(size), name3(size), name4(size); for(int i = 0; i < size; i++) IN(name1[i], name2[i], name3[i], name4[i]); #define VV(type, name, h, w) vector> name(h, vector(w));IN(name) int scan() { return getchar(); } void scan(int &a) { cin >> a; } void scan(long long &a) { cin >> a; } void scan(char &a) { cin >> a; } void scan(double &a) { cin >> a; } void scan(string &a) { cin >> a; } template void scan(pair &p) { scan(p.first), scan(p.second); } template void scan(vector &); template void scan(vector &a) {for(auto &i : a) scan(i);} template void scan(T &a) { cin >> a; } void IN() {} template void IN(Head &head, Tail &...tail) {scan(head);IN(tail...);} // tute7627 template using PQ = priority_queue; template using QP = priority_queue,greater>; templatevoid stout(const T &v,ll h,ll w){for(ll i=0;ivoid stout(const T &v,ll n){for(ll i=0;ivoid stout(const vector&v){stout(v,v.size());} templatevoid stout(const vector>&v){for(auto &vv:v)stout(vv,vv.size());} templatevoid debug(const T &v,ll h,ll w){for(ll i=0;ivoid debug(const T &v,ll n){for(ll i=0;ivoid debug(const vector&v){debug(v,v.size());} templatevoid debug(const vector>&v){for(auto &vv:v)debug(vv,vv.size());} templatevoid debug(stack st){while(!st.empty()){cerr<void debug(queue st){while(!st.empty()){cerr<void debug(deque st){while(!st.empty()){cerr<void debug(PQ st){while(!st.empty()){cerr<void debug(QP st){while(!st.empty()){cerr<void debug(const set&v){for(auto z:v)cerr<void debug(const multiset&v){for(auto z:v)cerr<void debug(const array &a){for(auto z:a)cerr<void debug(const map&v){for(auto z:v)cerr<<"["<void OUT(Head&& head, Tail&&... tail){cout << head;if(sizeof...(tail)) cout << " ";OUT(move(tail)...);} void ERR() {cerr << endl;} template void ERR(Head&& head, Tail&&... tail){cerr << head;if(sizeof...(tail)) cerr << " ";ERR(move(tail)...);} void fsp(int n){cout << fixed << setprecision(n);} templatebool chmax(T &a, const T &b) { if (abool chmin(T &a, const T &b) { if (b // using namespace atcoder; // using mint=modint998244353; // using mint=modint1000000007; int main(){ cin.tie(0); ios::sync_with_stdio(false); LL(n); VEC(ll,a,n); SORT(a); ll ans=0; map mp,pm; REP(i,n) mp[a[i]]++; REP(i,n){ if(mp.count(a[i]+1)&&mp.count(a[i])) pm[a[i]+2]+=mp[a[i]+1]*mp[a[i]]; if(mp.count(a[i]+1)&&pm.count(a[i])) pm[a[i]+2]+=mp[a[i]+1]*pm[a[i]]; } for(auto [u,v]:mp) ans+=v; for(auto [u,v]:pm) ans+=v; OUT(ans); }