figure img   {
  display: block;
    margin: auto;
}

body   {
    font-family: roboto;
    margin: 50px 50px 50px 50px;
    background-image: url(img/GRUPO.svg) no-repeat center center fixed;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}

body header {
    flex-direction: row;
    justify-content:space-around;
}

body header nav ul{
    display: flex;
    flex-direction: row;
    list-style: none;
    justify-content:space-around;
}

main   {
  margin: auto;
}

main h1  {
  text-align: center;
  background-color: #404040;
  border-radius: 5px;
  width: 450px;
  margin: auto;
  margin-top: 30px;
  margin-bottom: 30px;
  color: white;
  font-size: 22px;
}

body header nav ul li{
    display: flex;
    flex-direction: row;
    list-style: none;
    justify-content:space-around;
}

footer    {
    font-size: 9px;
    font-family: roboto;
    text-align: center;
    margin-right: 200px;
    margin-left: 200px;
}

.principal  {
    padding: 10px;
}

.img-border  {
  object-fit: cover;
  width: 250px;
  height: 250px;
  border-radius: 15px;
  margin-left: 30px;
}

.alumno  {
position: relative;
float: left;
text-align: center;
}

.alumno img  {
  -webkit-filter: grayscale(100%); /* Safari 6.0 - 9.0 */
      filter: grayscale(100%);
}

.alumno  a{
  color: #43abe1;
  text-decoration: none;
  font-weight: bolder;
  font-size: 20px;
}

.alumno  p{
  background-color: #404040;
  margin-left: 20px;
  border-radius: 5px;
}

nav    {
  background-color: #404040;
  border-color: #43abe1;
  height: 50px;
  border-radius: 15px;
  border-style: double;
}

Nav a{
     color: #f2f2f2;
     text-decoration: none;
     font-weight: bolder;
}

Nav a:hover {
    color: white;
    text-decoration: none;
}

.carta  {
  width: 50%;
}