#include #include #include #include #include #include #include #include #include #include using namespace std; #define FOR(i,a,b) for (int i=(a);i<(b);i++) #define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--) #define REP(i,n) for (int i=0;i<(n);i++) #define RREP(i,n) for (int i=(n)-1;i>=0;i--) #define inf INT_MAX/3 #define INF INT_MAX/3 #define PB push_back #define MP make_pair #define ALL(a) (a).begin(),(a).end() #define SET(a,c) memset(a,c,sizeof a) #define CLR(a) memset(a,0,sizeof a) #define pii pair #define pcc pair #define pic pair #define pci pair #define VS vector #define VI vector #define DEBUG(x) cout<<#x<<": "<b?b:a) #define MAX(a,b) (a>b?a:b) #define pi 2*acos(0.0) #define INFILE() freopen("in0.txt","r",stdin) #define OUTFILE()freopen("out0.txt","w",stdout) #define in scanf #define out printf #define ll long long #define ull unsigned long long #define eps 1e-14 #define FST first #define SEC second int bitcount(long bits) { bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555); bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333); bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f); bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff); return (bits & 0x0000ffff) + (bits >> 16 & 0x0000ffff); } int dpL[3001][3001]; int dpR[3001][3001]; int main(void) { int N; cin >> N; vector A; REP(i, N) { int a; cin >> a; A.push_back(a); } memset(dpL, -1, sizeof(dpL)); memset(dpR, -1, sizeof(dpR)); for (int i = 0; i < N; ++i) { dpL[i][i] = dpR[i][i] = 1; } int res = 0; for (int w = 1; w < N; ++w) { //幅で更新していくといい感じになった for (int l = 0; l < N - w; ++l) { int r = l + w; if (A[l] >= A[r]) dpL[l][r] = dpL[l][r - 1]; else { dpL[l][r] = max(dpL[l][r - 1], dpR[l + 1][r] + 1); } if (A[l] <= A[r]) dpR[l][r] = dpR[l + 1][r]; else { dpR[l][r] = max(dpR[l + 1][r], dpL[l][r - 1] + 1); } res = max(res, dpL[l][r]); res = max(res, dpR[l][r]); } } cout << res << endl; return 0; }