import java.io.*; import java.util.*; import java.util.function.BiFunction; import static java.lang.Math.*; import static java.lang.String.format; public class Main { public static void main(String[] args) { solve(); } final static int INF = Integer.MAX_VALUE>>1; final static int MOD = 1_000_000_007; final static int[] dx4 = { 0, 1, 0, -1 }; final static int[] dy4 = { 1, 0, -1, 0 }; final static int[] dx8 = {0, 1, 1, 1, 0, -1, -1, -1}; final static int[] dy8 = {1, 1, 0, -1, -1, -1, 0, 1}; public static void solve(){ //TODO:Solve problem like *** Scanner sc=new Scanner(); int n=sc.nextInt(); int[] value=new int[n]; for (int i = 0; i < n; i++) { value[i]=sc.nextInt(); } int[][] dp=new int[3][n+2]; dp[0][2]=value[0]; dp[1][2]=value[0]; dp[2][2]=0; for (int i = 3; i < n+2; i++) { // dp[0][i] = max(dp[0][i - 2] + value[i-2], max(dp[1][i - 3] + value[i-2], dp[2][i - 1])); // dp[1][i] = max(dp[0][i - 2] + value[i-2], max(dp[1][i - 3] + value[i-2], dp[2][i - 1])); // dp[2][i] = max(dp[0][i - 2] + value[i-2], max(dp[1][i - 3] + value[i-2], dp[2][i - 1])); dp[0][i]=max(dp[0][i-2],max(dp[1][i-2],dp[2][i-2]))+value[i-2]; dp[1][i]=max(dp[0][i-3],max(dp[1][i-3],dp[2][i-3]))+value[i-2]; dp[2][i]=max(dp[0][i-1],max(dp[1][i-1],dp[2][i-1])); } put(max(dp[0][n + 1], max(dp[1][n + 1], dp[2][n + 1]))); } private static abstract class SegmentTree { private final int originSize; private final int height; private final long[] node; private final long noRelationVal; protected SegmentTree (long[] original,long noRelationVal){ this.noRelationVal=noRelationVal; originSize = original.length; { int height_ = 1; while (originSize > (1 << (height_ - 1))) { height_++; } height = height_; } this.node = new long[ (1<=0; i--){ this.node[i]=marge(this.node[i*2+1],this.node[i*2+2]); } } public long getVal(int a,int b){ return getVal(a,b,0,0,-1); } public long getVal(int a, int b, int k, int l, int r) { //node[k]=origin上の範囲[l,r]の合計を表している if(r < 0) r = (1<<(height-1))-1; if(b=originSize) throw new IllegalArgumentException(format("挿入位置が不正%d",index)); index=(1<<(height-1))-1+index; node[index]=val; while(index>0){ index=(index-1)/2; node[index]=marge(node[2*index+1],node[2*index+2]); } } protected abstract long marge(long a,long b); @Override public String toString(){ StringBuilder result=new StringBuilder(); result.append(format("Class:%s\n",getClass().getSimpleName())); result.append(format("height:%d\n",height)); for(int currentHeight=1;currentHeight<=height;currentHeight++){ for(int i=(1<<(currentHeight-1))-1;i<=(1< Integer.MAX_VALUE) throw new NumberFormatException(); return (int) nl; } public double nextDouble() { return Double.parseDouble(next()); } } final static private class FixedIntPair { final public int x, y; final static public FixedIntPair ZEROS=new FixedIntPair(0,0); FixedIntPair(int x, int y) { this.x = x; this.y = y; } public static double distance(FixedIntPair fip1,FixedIntPair fip2){ double x = (double) fip1.x - fip2.x; double y = (double) fip1.y - fip2.y; return Math.sqrt(x*x+y*y); } @Override public int hashCode() { return x*100000+y; } @Override public boolean equals(Object obj) { if(obj==null)return false; if(!(obj instanceof FixedIntPair)) return false; FixedIntPair pair=(FixedIntPair) obj; return this.x==pair.x&&this.y==pair.y; } @Override public String toString() { return format(FixedIntPair.class.getSimpleName()+":(%d,%d)", x, y); } } final static private class FixedLongPair { final public long x, y; final static public FixedLongPair ZEROS=new FixedLongPair(0,0); FixedLongPair(long x, long y) { this.x = x; this.y = y; } public static double distance(FixedLongPair flp1,FixedLongPair flp2){ double x = (double) flp1.x - flp2.x; double y = (double) flp1.y - flp2.y; return Math.sqrt(x*x+y*y); } @Override public int hashCode() { return (int)x+(int)y; } @Override public boolean equals(Object obj) { if(obj==null)return false; if(!(obj instanceof FixedLongPair)) return false; FixedLongPair pair=(FixedLongPair)obj; return this.x==pair.x&&this.y==pair.y; } @Override public String toString() { return format(FixedLongPair.class.getSimpleName()+":(%d,%d)", x, y); } } final static private class Binary{ public static String toZeroPadding(int i){ return format("%"+Integer.toBinaryString(-1).length()+"s",Integer.toBinaryString(i)).replace(' ','0'); } public static String toZeroPadding(long i){ return format("%"+Long.toBinaryString(-1).length()+"s",Long.toBinaryString(i)).replace(' ','0'); } } final static private class Util { static long gcd(long a,long b){ a= abs(a); b= abs(b); if(a=0&&i=0&&j