function checkStage () public returns (Stage) {

    require (stage != Stage.LIFE);
    
    Stage currentStage = stage;
    if (currentStage == Stage.ICO) {
        if (block.timestamp >= LIFE_START_TIME || tokenICO > LIFE_START_TOKENS) {
            currentStage = Stage.LIFE;
            stage = Stage.LIFE;
        }
    else return currentStage;
    }
    return currentStage;
}