my_str=99999999999999999999 
b=c*c=9999999999999999999800000000000000000001 
d=(a=b+b)/c=199999999999999999998 
d=gcd(a,c)=99999999999999999999 
d_binary=1010110101111000111010111100010110101100011000011111111111111111111