#include #define EPS 1e-9 #define INF 1070000000LL #define MOD 1000000007LL #define fir first #define foreach(it,X) for(auto it=(X).begin();it!=(X).end();it++) #define numa(x,a) for(auto x: a) #define ite iterator #define mp make_pair #define rep(i,n) rep2(i,0,n) #define rep2(i,m,n) for(int i=m;i<(n);i++) #define pb push_back #define pf push_front #define sec second #define sz(x) ((int)(x).size()) #define ALL( c ) (c).begin(), (c).end() #define gcd(a,b) __gcd(a,b) #define mem(x,n) memset(x,n,sizeof(x)) #define endl "\n" using namespace std; template void deploy(std::ostream &os, const TUPLE &tuple){} template void deploy(std::ostream &os, const TUPLE &t){ os << (POS == 0 ? "" : ", ") << get(t); deploy(os, t); } template std::ostream& operator<<(std::ostream &os, std::pair &p){ os << "(" << p.first <<", " << p.second <<")";return os; } template std::ostream& operator<<(std::ostream &os, std::vector &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; } template std::ostream& operator<<(std::ostream &os, std::set &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; } template std::ostream& operator<<(std::ostream &os, std::map &mp){ int remain = mp.size(); os << "{"; for(auto e: mp) os << "(" << e.first << " -> " << e.second << ")" << (--remain == 0 ? "}" : ", "); return os; } #define DEBUG1(var0) { std::cerr << (#var0) << "=" << (var0) << endl; } #define DEBUG2(var0, var1) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG1(var1); } #define DEBUG3(var0, var1, var2) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG2(var1,var2); } #define DEBUG4(var0, var1, var2, var3) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG3(var1,var2,var3); } using ll = long long; int N; int nums[3030]; int memo[3030][3030][2]; int dp_go(int x, int y, bool high) { if (x == y) { return 1; } if (memo[x][y][high] >= 0) { return memo[x][y][high]; } int ret = 0; if (high) {// x < y if (nums[x] < nums[y]) { ret = 1 + dp_go(x+1,y,false); } ret = max(ret, dp_go(x,y-1,high)); }else { //x > y if (nums[x] > nums[y]) { ret = 1 + dp_go(x,y-1,true); } ret = max(ret, dp_go(x+1,y,high)); } //DEBUG3(x,y,ret) return memo[x][y][high] = ret; } int main() { cin.tie(0); ios_base::sync_with_stdio(0); cin >> N; rep(i,N){ cin >> nums[i]; } mem(memo,-1); int ans = 0; rep(i,N) { rep2(j,i,N){ //DEBUG2(i,j); ans = max(ans, dp_go(i,j,true)); } } cout << ans << endl; return 0; }