Thread: length of input number

I made a loop to return the number of digit entered by a user, but the problem is that loop does not work with big numbers like number which is more than 10 digit, I also used the sizeof() function but it is the same. Is there any Idea how to make it read bigger numbers, Thanks and the loop is :

Code:

cout<<"Please enter the number :"<<endl; //getting input
    cin>>num;

    temp1=num;
	count=0;

	

    while (temp1!=0){                      //counting number of digits
       temp1=temp1/10;
       count=count+1;	     
       }