#include<bits/stdc++.h>
using namespace std;
long long n,a[200005],b[200005],ps,c[200005],s1,s2,s;
int main(){
    freopen("matHS.in","r",stdin);
    freopen("matHS.out","w",stdout);
    scanf("%lld",&n);
    for(int i=1;i<=n;i++){
        scanf("%lld",&a[i]);
        b[i]=a[i];
    }
    sort(b+1,b+n+1);
    ps=unique(b+1,b+n+1)-b-1;
    for(int i=1;i<=ps;i++){
        s1=s2=0;
        for(int j=1;j<=n;j+=2){
            if(a[j]==b[i]) s1++;
        }
        for(int j=2;j<=n;j+=2){
            if(a[j]==b[i]) s2++;
        }
        s=max(s,max(s1,s2)+b[i]*2);
    }
    printf("%lld",s);
	return 0;
}