IEEE 754 addition wrong result floating point numbers


I want to add two IEEE 754 numbers.
I followed the steps to add two 754 numbers. However the result it not correct.
Number 1:
S:0
E:01111111
M:11111111111111111111111

Number 2:
S:0
E:01111111
M:00000000000000000000000

Here is my calculation:

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The site http://weitz.de/ieee/ gives this result:
S: 0
E: 10000000
M: 10000000000000000000000

in my calculation the mantissa is 01111…
Why?