#include<bits/stdc++.h>
#define rep(i, l, r) for(int i = (l); i <= (r); i ++)
#define per(i, r, l) for(int i = (r); i >= (l); i --)
#define trv(i, u, v) for(int i = head[u], v = e[i].to; i; v = e[i = e[i].nxt].to)
#define fi first
#define se second
#define all(s) s.begin(), s.end()
#define sz(s) (int)(s.size())
#define lb(s) ((s) & -(s))
#define pb push_back
using namespace std;

typedef long long ll;
typedef pair<int, int> P;
mt19937_64 hua(time(0));
template<typename T> inline bool chkmx(T &x, T y) {return x < y ? x = y, 1 : 0;}
template<typename T> inline bool chkmn(T &x, T y) {return y < x ? x = y, 1 : 0;}
template<int T> using A = array<int, T>;

inline int read() {
	int x = 0, f = 1; char c = getchar();
	for(; !isdigit(c); c = getchar()) if(c == '-')  f = 0;
	for(; isdigit(c); c = getchar()) x = x * 10 + c - '0';
	return f ? x : -x;
}
const int maxn = 4000;
const int maxm = 4000000;
int n, w[maxn + 5][maxn + 5]; 
bitset<maxn + 5> f[maxn + 5], g[maxn + 5], cur[maxn + 5];
A<3> s[maxm + 5];
int tp;
inline void seta(int l, int r) {
	f[l][r] = g[r][l] = 1;
	if(cur[l - 1][r + 1] && !f[l  - 1][r + 1]) seta(l - 1, r + 1);
	bitset<maxn + 5> x = f[r + 1] & ~f[l];
	for(int p = x._Find_first(); p <= n; p = x._Find_next(p)) seta(l, p); 
	bitset<maxn + 5> y = g[l - 1] & ~g[r];
	for(int p = y._Find_first(); p <= n; p = y._Find_next(p)) seta(p, r); 
}
int main() {
	//freopen("in.txt", "r", stdin);
	n = read();
	rep(i, 1, n) for(int j = i + 1; j <= n; j += 2) w[i][j] = read(), s[++ tp] = {w[i][j], i, j};
	sort(s + 1, s + tp + 1);	
	rep(i, 0, n) g[i][i + 1] = f[i + 1][i] = 1;
	rep(i, 1, tp) { 
		int l = s[i][1], r = s[i][2];
		cur[l][r] = 1;
		if(!f[l][r] && f[l + 1][r - 1]) seta(l, r);
		if(f[1][n]) {
			cout << s[i][0] << '\n';
			return 0;
		}
	}
	return 0;
}