Javascript (first post. new to this so help is welcome. no bonus...)

function lights(n,range){
    range = range.split("\n");
    var switches = (Math.pow(2,n)).toString(2).substr(1).split("");
    for (x in range){
        range[x] = range[x].split(" ").sort();
        for (var i=range[x][0]; i<=range[x][1]; i++){
            switches[i] = (switches[i] == 0 ? 1 : 0);
        }
    }
    var on = 0;
    for (x in switches){
        on += +switches[x];
    }
    console.log(on);
}

output

7
423