Given an input string, generate a variable name out of it in easy to read format by a programmer.

If the input string contains any special character other than ('_'), replace it with ('_') and then return it in readable format variable name.

Example

 input = 'this is an input var'
 output = 'thisIsAnInputVar'

Another example

 input = 'this one has special char @123'
 output = 'thisOneHasSpecialChar_123'