<div id="wrap">
  <div class="center">
    <div class="section">

      <div class="input">
        <span>+7</span>
        <input type="tel">
      </div>

    </div>
  </div>
</div>

// autoprefixer: true

html,
body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  font-size: 16px;
  line-height: 1.4;
  color: #555;
  background: #fff;
}

* {
  box-sizing: border-box;
}

#wrap {
  position: relative;
  padding-top: 60px;
  transition: padding-top .3s ease;
}

.section {
  padding: 40px;
}

.center {
  width: 100%;
  max-width: 1200px;
  margin: auto;
}

.input {
  position: relative;
  width: 180px;
  height: 42px;
  
  span {
    display: block;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    width: 30px;
    line-height: 42px;
    text-align: center;
    font-size: 14px;
    border-right: 1px solid #eee;
  }
}

input {
  width: 100%;
  height: 100%;
  border: 0;
  background: #fff;
  padding: 0 10px 0 40px;
  font-size: 14px;
  box-shadow: 0 0 0 1px #aaa;
  transition: box-shadow .1s ease;
  outline: none;
  
  &:focus {
    box-shadow: 0 0 0 2px #777;
  }
}

$(function () {

  $('input').on('keyup change', function () {
    var $input = $(this),
      inputVal = $input.val();

    if (inputVal[0] == 8 && inputVal.length > 10) {
      inputVal = $input.val().substring(1);
    }
    
    $input.val(inputVal.replace(/\s+/g, ' ').trim());
  });
});