Javascript-форум - Я новичок помогите.

Выдает ошибку - script.js:3 Uncaught TypeError: Cannot read property 'checked' of null.Спасибо профи.
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Вероятность СOVID 19</title>
</head>
<body>
    <form>
    <p><b>Возраст.</b></p>
    <input id="v1"/><p></p>        
    <p><b>Пол</b></p>
    <p><input name="dzen" type="radio" value="nedzen1">М</p>
    <p><input name="dzen" type="radio" value="nedzen2">Ж</p>
    </form>
    <p><b>Хроническое заболевание сердца</b></p>
    <form>
    <p><input name="dzen" type="radio" value="nedzen3">Да</p>
    <p><input name="dzen" type="radio" value="nedzen4" checked>Нет</p>
</form>
    <form>
    <p><b>Хроническое заболевание почек</b></p>
    <p><input name="dzen" type="radio" value="nedzen5">Да</p>
    <p><input name="dzen" type="radio" value="nedzen6" checked>Нет</p>
</form>
<form>
    <p><b>Сахарный диабет</b></p>
    <p><input name="dzen" type="radio" value="nedzen7">Да</p>
    <p><input name="dzen" type="radio" value="nedzen8" checked>Нет</p>
</form>
<form>
    <p><b>Деменция</b></p>
    <p><input name="dzen" type="radio" value="nedzen9">Да</p>
    <p><input name="dzen" type="radio" value="nedzen10" checked>Нет</p>
</form>
<form>
    <p><b>Гипертензия</b></p>
    <p><input name="dzen" type="radio" value="nedzen11">Да</p>
    <p><input name="dzen" type="radio" value="nedzen12" checked>Нет</p>
</form>
    <button onclick="cop()">Расчитать вероятность COVID 19</button>
    <p id="resultat"></p>
    <script>function cop() {
        const v1 = document.getElementById("v1").value;
        if(document.getElementById('nedzen1').checked == true){
        const p1 = 1;
        };
        if(document.getElementById('nedzen2').checked == true){
            const p1 = 0;
        };
        if(document.getElementById('nedzen3').checked == true){
            const p2 = 1;
            };
        if(document.getElementById('nedzen4').checked == true){
                const p2 = 0;
        };
        if(document.getElementById('nedzen5').checked == true){
            const p3 = 1;
            };
        if(document.getElementById('nedzen6').checked == true){
                const p3 = 0;
            };
        if(document.getElementById('nedzen7').checked == true){
                const p4 = 1;
                };
        if(document.getElementById('nedzen8').checked == true){
                    const p4 = 0;
                };
        if(document.getElementById('nedzen9').checked == true){
                    const p5 = 1;
                    };
        if(document.getElementById('nedzen10').checked == true){
                        const p5 = 0;
                    };
        if(document.getElementById('nedzen11').checked == true){
                        const p6 = 1;
                        };
        if(document.getElementById('nedzen12').checked == true){
                            const p6 = 0;
                        };
        const X1 = 6.903 + 0.047 * v1;
        const X2 = 0.553 * pol1;
        const X3 = 0.614 * pol2;
        const X4 = 0.536 * pol6;
        const X5 = 1.149 * pol3;
        const X6 = 0.734 * pol4;
        const X7 = 1.03 * pol5;
        const X = X1 + X2 + X3 + X4 + X5 + X6 + X7;
        const S = 1+Math.exp(-X);
        const Y = 1/(1+S);
        if (Y > 0.044) {
            const rez = "Прогноз : смерть.";
        }else{
            const rez = "Прогноз : жизнь.";
        };
        document.getElementById("resultat").innerHTML = rez;
    };</script>
</body>
</html>