codeforces

#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <cmath>
#define INF 0x3fffffff
#define JIN 678
#define mst(a,b) memset(a,b,sizeof(a))
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int maxn=1e5+5;
char str[60];
char ans[2000];
int ()
{
    int n;
    cin>>n;
    getchar();
    scanf("%s",str);
    int idx=0;
    int j;int i;
    int cnt=0;
    for(i=0,j=0;i<n;j++,i+=j)
        ans[cnt++]=str[i];
    for(int idx=0;idx<cnt;idx++)
        printf("%c",ans[idx]);
    cout<<'n';
    return 0;
}