body { 
      background:darkred;
      font-family: Arial;
      }

header {
    text-align: center;
    background-color: darkslategrey;
    margin: 3rem 10rem 3rem 10rem;
    padding: 1rem;
    color:cornsilk;
}

.pie {font-stretch: expanded;
    font-size: 1.2rem;
    text-align: center;
}

.footerestilo {
    font-style: italic;
    font-size: 0.6rem; 
    margin: 3rem 10rem 3rem 10rem; 
    background-color: darkred;
    color: aliceblue;
    padding: 2rem;
    text-align: center;
}

nav ul{
    list-style-type: none;
}
nav ul li a{
    position: relative;
    float:right;
    padding:1rem;
    text-decoration:none;
    color:aliceblue;
    background-color:darkred;
    margin:2rem;
    color:cornsilk;
}
.materias{margin: 1rem 8.5rem 1rem 5rem;
    color: aliceblue;
    text-align: center;
}