#include <bits/stdc++.h>
using namespace std;const int maxn = 1e5 + 10;
char s[maxn], len;int main() {scanf("%d", &len);scanf("%s", s);int p = 0;for(int i = 0; i < len; i = i + p) {printf("%c", s[i]);p++;}printf("\n");return 0;
}

#include <bits/stdc++.h>
using namespace std;const int maxn = 1e5 + 10;
int a[maxn], n;int main() {scanf("%d", &n);for(int i = 1; i <= n; i ++) {scanf("%d", &a[i]);}sort(a + 1, a + 1 + n);printf("%d\n", min(a[n - 1] - a[1], a[n] - a[2]));return 0;
}

#include <bits/stdc++.h>
using namespace std;int n, k;priority_queue<int> Q;int cnt_Q;int main() {scanf("%d%d", &n, &k);for(int i = 29; i >= 0; i --) {if(n >= (1 << i)) {Q.push(i);cnt_Q ++;n -= (1 << i);}}if(cnt_Q > k) {printf("NO\n");return 0;}while(cnt_Q < k) {int tp = Q.top();if(tp == 0) {printf("NO\n");return 0;}Q.pop();Q.push(tp - 1);Q.push(tp - 1);cnt_Q ++;}printf("YES\n");while(!Q.empty()) {int tp = Q.top();printf("%d ", 1 << tp);Q.pop();}return 0;
}

#include <bits/stdc++.h>
using namespace std;const int maxn = 2e5 + 10;int n;
int a[maxn];int b[maxn][5];int flag;void dfs(int x) {int num1 = b[a[x]][1];int num2 = b[a[x]][2];if(b[num1][1] == num2 || b[num1][2] == num2) {a[x + 1] = num1;a[x + 2] = num2;if(x == n - 2) {flag = 1;return;}dfs(x + 1);if(flag) return;}if(b[num2][1] == num1 || b[num2][2] == num1) {a[x + 1] = num2;a[x + 2] = num1;if(x == n - 2) {flag = 1;return;}dfs(x + 1);if(flag) return;}
}int main() {scanf("%d", &n);for(int i = 1; i <= n; i ++) {scanf("%d%d", &b[i][1], &b[i][2]);}flag = 0;a[1] = 1;dfs(1);for(int i = 1; i <= n; i ++) {printf("%d ", a[i]);}printf("\n");return 0;
}

#include <bits/stdc++.h>
using namespace std;const int maxn = 1e6 + 10;int n;
int a[maxn], b[maxn], c[maxn];
char s[maxn];int main() {scanf("%d", &n);scanf("%s", s);for(int i = 1; i <= n; i ++) {a[i] = (s[i - 1] == '(') ? 1 : -1;}for(int i = 1; i <= n; i ++) {a[i] += a[i - 1];}c[1] = a[1];for(int i = 2; i <= n; i ++) {c[i] = min(a[i], c[i - 1]);}b[n] = a[n];for(int i = n - 1; i >= 1; i --) {b[i] = min(a[i], b[i + 1]);}for(int i = 1; i <= n; i ++) {// printf("[i: %d]  a: %d, b: %d, c: %d\n", i, a[i], b[i], c[i]);}int ans = 0;for(int i = 1; i <= n; i ++) {if(s[i - 1] == '(') {if(c[i - 1] >= 0 && b[i] - 2 >= 0 && a[n] - 2 == 0) ans ++;} else {if(c[i - 1] >= 0 && b[i] + 2 >= 0 && a[n] + 2 == 0) ans ++;}}printf("%d\n", ans);return 0;
}

#include <bits/stdc++.h>
using namespace std;const int maxn = 4e5 + 10;
struct Edge {int x, y;long long w;
}e[maxn];
int cnt_e;int n, m;
long long a[maxn];int f[maxn];bool cmp(const Edge& a, const Edge& b) {return a.w < b.w;
}int Find(int x) {if(x != f[x]) f[x] = Find(f[x]);return f[x];
}int main() {scanf("%d%d", &n, &m);for(int i = 1; i <= n; i ++) {scanf("%lld", &a[i]);f[i] = i;}int index = 1;for(int i = 2; i <= n; i ++) {if(a[i] < a[index]) {index = i;}}for(int i = 1; i <= n; i ++) {if(i == index) continue;e[cnt_e].x = i;e[cnt_e].y = index;e[cnt_e].w = a[i] + a[index];cnt_e ++;}while(m--) {scanf("%d%d%lld", &e[cnt_e].x, &e[cnt_e].y, &e[cnt_e].w);cnt_e ++;}sort(e, e + cnt_e, cmp);long long ans = 0;for(int i = 0; i < cnt_e; i ++) {int fx = Find(e[i].x);int fy = Find(e[i].y);if(fx == fy) continue;ans = ans + e[i].w;f[fx] = fy;}printf("%lld\n", ans);return 0;
}