#include<assert.h>

#pragma CIVL ACSL
$input int N;
$assume(0 < N);
int a[N];
int b[N];

int main() {

  int x = 1;
  //@ focus I;
  /*@ loop invariant x == i+1;
    @*/
  for (int i = 0; i < N; i++) {
    a[i] = i + x;
    x = x+1;
  }

  //@ focus I;
  for (int i = 0; i < N; i++) {
    b[i] = i;
  }

  //@ focus I;
  for (int i = 0; i < N; i++) {
    a[i] = a[i] * b[i];
  }
  
  //@ focus I;
  $assert($forall(int i:0..N-1) a[i] == (2*i+1)*i);
}