#pragma TASS input 
int N_BOUND;
#pragma TASS input {N>=0 && N<=N_BOUND} 
int N;
#pragma TASS output 
int s;

void main() {
  int j=0;
  int i=0;

  l:
  #pragma TASS jointinvariant @main {2:1  j == spec.i && i == spec.j && j%2 == 0}
  while (j < 2 * N) 
  {
    i = i + j;
    j = j + 2;
  }
  s = i;
}
