5RE 求助

#include<iostream>
using namespace std;
int a[5000005];
int n,k;
int bsort(int l,int r){
    int i=l,j;
    for(int m=l+1;m<=r;m++){
        if(a[l]>a[m]){
            i++;
            swap(a[m],a[i]);
        }else if(a[l]<a[m]) swap(a[m],a[i+1]);
    }
    swap(a[l],a[i]);
    if(k<i) bsort(0,i-1);
    else if(k>i) bsort(i+1,r);
    else return a[k];
}
int main(){
    scanf("%d%d",n,k);
    for(int i=0;i<n;i++){
        scanf("%d",a[i]);   
    }
    printf("%d",bsort(0,n-1));
    return 0;
}