var arr = document.querySelectorAll('.mn');
var obj = {};

for(var i=0; i<arr.length; i++) {
    var login = arr[i].innerHTML.substring(4, arr[i].innerHTML.length - 4);
    if(!obj[login])
        obj[login] = 1;
    else
        obj[login]++;

}
console.log(arr.length, obj);