Auto increment value in element id

I am trying to get value of dynamic generated inputs. Here is my code and what I want actually

Here is my Code:

function activehead_standard(){
var cnt = 4;
for(i=1;i<=cnt;i++){
var active_head = document.getElementById('standard_'.i).value;

}

}

I want to get values of input: standard_1 standard_2 standard_3 standard_4

but its not getting the value of input through ids I am sure its actually not getting the ids of inputs