function cont(per) {
var obl = document.getElementById(per)
var span = document.getElementsByTagName('span')
for (i=0; i<span.length; i++) {
span[i].style.display = ('none')
}
if (obl.style.display == 'block') {
obl.style.display = ('none')
}
else {
obl.style.display = ('block')
}
}