#include <math.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <assert.h> #include <limits.h> #include <stdbool.h> long int sumOfGroup(int k) { // Return the sum of the elements of the k'th group. long grp=((k*(k+1))/2); int cnt=1; long sum=0; long ele=++grp;; while(cnt<=k) { sum+=ele; ++cnt; ele+=2; } return sum; } int main() { int k; scanf("%i", &k); long int answer = sumOfGroup(k); printf("%ld\n", answer); return 0; }