1+2+3+4+5+6+7+8+9.+9999999
=(1+10000000)*10000000/2-10000000
=10000001*5000000-10000000
=50000005000000-10000000
=49999995000000
1+2+3+4+5+6+7+8+9.+9999999
=(1+10000000)*10000000/2-10000000
=10000001*5000000-10000000
=50000005000000-10000000
=49999995000000