Hacking with the program to find the greatest common factor

$./app 
Sign detection [1] 
Power of two [2] 
Counting No. of bits set [3] 
Set or clear bits without branching[4] 
Find maximum value[5] 
Finding least common multiple[6] 
Finding the greatest commom divisor[7] 
7
Enter the two values for finding GCD: 12 6
GCD is: 6
$./app 
Sign detection [1] 
Power of two [2] 
Counting No. of bits set [3] 
Set or clear bits without branching[4] 
Find maximum value[5] 
Finding least common multiple[6] 
Finding the greatest commom divisor[7] 
7
Enter the two values for finding GCD: 5 12
GCD is: 1
$./app 
Sign detection [1] 
Power of two [2] 
Counting No. of bits set [3] 
Set or clear bits without branching[4] 
Find maximum value[5] 
Finding least common multiple[6] 
Finding the greatest commom divisor[7] 
7
Enter the two values for finding GCD: 20 25
GCD is: 5
$./app 
Sign detection [1] 
Power of two [2] 
Counting No. of bits set [3] 
Set or clear bits without branching[4] 
Find maximum value[5] 
Finding least common multiple[6] 
Finding the greatest commom divisor[7] 
7
Enter the two values for finding GCD: 12 8
GCD is: 4
$./app 
Sign detection [1] 
Power of two [2] 
Counting No. of bits set [3] 
Set or clear bits without branching[4] 
Find maximum value[5] 
Finding least common multiple[6] 
Finding the greatest commom divisor[7] 
7
Enter the two values for finding GCD: 32 235
GCD is: 1
$