.center{
    margin-top: 150px;
 display: grid;
}
.a{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.b{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.c{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.d{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.e{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.f{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.g{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.h{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.i{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.j{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.k{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.l{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}
.m{
    margin-left: auto;
    margin-right: auto;
    margin-bottom: 30px;
}