int main() {
  int i, n, nextTerm, t1, t2;

  i = 0;
  n = 20; // put here the number you want !

  t1 = 0;
  t2 = 1;

  nextTerm = t1 + t2;

  n = n - 3; // cause nextTerm already contains the 3rd term
  while (i <= n){
    t1 = t2;
    t2 = nextTerm;
    nextTerm = t1 + t2;
    i = i+1;
  }
}