cat O(n)

#include<stdio.h>
typedef long long int ll;
int main()
{
    int n;
    scanf("%d",&n);

    ll prev = -1;
    ll ans = 0;
    for(int i = 0 ; i < n ; i ++){
        ll size;
        scanf("%lld",&size);
        if(size <= ans){
            continue;
        }
        else if(prev == -1){
            prev = size;
        }
        else{
            if(size == prev){
                prev = -1;
            }
            else if(size > prev){
                if(prev > ans)ans = prev;
                prev = size;
            }
            else{
                if(size > ans)ans = size;
            }
        }
    }
    printf("%lld",ans);
    return 0;
}