solution

function nbYear(p0, percent, aug, P) {
    // your code
    var numYears = 0;
    var currentPop = p0;
    var convertPercent;
    
    if (percent === null || percent == 0) {
      convertPercent = 0;
    } else {
      convertPercent = percent * .01;
    };
    
    while (currentPop < P) {
      currentPop = currentPop + (currentPop * convertPercent) + aug;
      numYears += 1;
    }
    
    return numYears;
}