Lang:G++
Edit1234567891011121314151617#include <bits/stdc++.h>#define sc scanf#define pf printfusing namespace std;int main(){int a[100000], n, k;while( ~sc("%d%d", &n, &k) ){k--;for(int i=0; i<n; i++) sc("%d", &a[i]);if( k<0 || k>=n ) k = -1;else nth_element( a, a+k, a+n);pf("%d\n", k==-1?-1:a[k]);}}