document.addEventListener('input', function(e) {
if (e.target.tagName !== 'INPUT' || e.target.type !== 'tel') return;
let val = e.target.value.replace(/D/g, '');
if (val.length > 0) {
if (val[0] == '8') val = '7' + val.slice(1);
else if (val[0] != '7') val = '7' + val;
}
val = val.slice(0, 11);
let f = '+7';
if (val.length > 1) f += ' (' + val.slice(1, 4);
if (val.length > 4) f += ') ' + val.slice(4, 7);
if (val.length > 7) f += '-' + val.slice(7, 9);
if (val.length > 9) f += '-' + val.slice(9, 11);
e.target.value = f;
}, true);
document.addEventListener('focus', function(e) {
if (e.target.tagName !== 'INPUT' || e.target.type !== 'tel') return;
if (e.target.value == '+7' || e.target.value == '') e.target.value = '';
}, true);