// Source: Antoine Miné: "Tutorial on static inference of numeric invariants by abstract interpretation", FTPL 2017.
// Example 4.7.

#include <assert.h>
extern void abort(void);
void reach_error() { assert(0); }
void __VERIFIER_assert(int cond) { if(!(cond)) { ERROR: {reach_error();abort();} } }
extern _Bool __VERIFIER_nondet_bool();

int main() {
  int x = 0;
  while (__VERIFIER_nondet_bool() == 0) {
    __VERIFIER_assert(0 <= x);
    __VERIFIER_assert(x <= 40);
    if (__VERIFIER_nondet_bool() == 0) {
      x++;
      if (x > 40)
        x = 0;
    }
  }
  return 0;
}