#pragma comment(linker, "/STACK:1024000000,1024000000")#include<cstdio>#include<cstring>#include<cmath>#include<algorithm>#include<vector>#include<map>#include<set>#include<queue>#include<stack>#include<iostream>using namespace std;typedef long long LL;const double pi=acos(-1.0),eps=1e-6;void File(){    freopen("D:\\in.txt","r",stdin);    freopen("D:\\out.txt","w",stdout);}template <class T>inline void read(T &x){    char c=getchar(); x=0;    while(!isdigit(c)) c=getchar();    while(isdigit(c)) {x=x*10+c-‘0‘; c=getchar();}}int n,k;int a[100010];int main(){    scanf("%d%d",&n,&k);    for(int i=1;i<=n;i++) scanf("%d",&a[i]);    int L=1,R=n,pos;    while(L<=R)    {        int mid=(L+R)/2;        LL num=(LL)(1+mid)*(LL)mid/(LL)2;        if(num>=(LL)k) R=mid-1,pos=mid;        else L=mid+1;    }    k=k-(1+pos-1)*(pos-1)/2;    printf("%d\n",a[k]);    return 0;}