while(true){
    aleatorio = Math.random();
    numero = Math.round(aleatorio * 4);

    if (numero == 0){
    imagen = "http://img6.imagebanana.com/img/tam409qu/sq_blue3.png";
    break;}

    if (numero == 1){
    imagen = "http://img6.imagebanana.com/img/kdm6vpkj/sq_blue.png";
    break;}

    if (numero == 2){
    imagen = "http://img6.imagebanana.com/img/xdcsddal/sq_blue2.png";
    break;}

    if (numero == 3){
    imagen = "http://img6.imagebanana.com/img/tam409qu/sq_blue3.png";
    break;}



    }
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