#include #include using namespace std; typedef unsigned long long _ulong; typedef long long int lint; typedef pair plint; typedef pair pld; #define ALL(x) (x).begin(), (x).end() #define SZ(x) ((lint)(x).size()) #define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i=i##_begin_;i--) #define REP(i, n) FOR(i,0,n) #define IREP(i, n) IFOR(i,0,n) #define endk '\n' templatebool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; } templatebool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; } lint gcd(lint a, lint b) { if (b == 0) return a; else return gcd(b, a % b); } lint ceil(lint a, lint b) { return (a + b - 1) / b; } lint digit(lint a) { return (lint)log10(a); } const lint MOD = 1e9 + 7, INF = 1e18; lint dx[8] = { 1, 0, -1, 0, 1, -1, 1, -1 }, dy[8] = { 0, 1, 0, -1, -1, -1, 1, 1 }; void YN(bool flag) { cout << (flag ? "YES" : "NO") << endk; } typedef pair Pa; typedef pair tlint; struct edge { lint v; lint a, b; }; lint N, A; int main() { cin >> N; map mp; REP(i, N) { cin >> A; mp[A]++; } lint maxv = 0; vector vec; for (plint v : mp) vec.push_back(v); vec.push_back({ INF, 0 }); REP(i, SZ(vec) - 1) { if (vec[i].first + 1 == vec[i + 1].first) { chmax(maxv, vec[i].second + vec[i + 1].second); } else { chmax(maxv, vec[i].second); } } cout << maxv << endk; }