let rec aux_simple = (i: int): int => 
  if (i < 100) {
    aux_simple(i + 1)
  } else {
    i
  };

let counter_simple = (n: int): int => aux_simple(n);

type sum_aggregator = {counter: int, sum: int };

let counter = (n: int): int => {
  let initial: sum_aggregator = {
    counter: 0,
    sum: 0
  };
  let rec aggregate = (prev: sum_aggregator): int => 
    if (prev.counter <= n) {
    
      
      aggregate({
          counter: prev.counter + 1,
          sum: prev.counter + prev.sum
        })
    } else {
      prev.sum
    };
  aggregate(initial)
};

let rec aux_nest = (prev: sum_aggregator): sum_aggregator => 
  if (prev.counter < 100) {
  
    let sum: int = prev.sum + aux_simple(prev.counter);
    aux_nest({counter: prev.counter + 1, sum: sum })
  } else {
    ({counter: prev.counter, sum: prev.sum })
  };

let counter_nest = (n: int): int => {
  let initial: sum_aggregator = {
    counter: 0,
    sum: 0
  };
  let out: sum_aggregator = aux_nest(initial);
  out.sum
};