Solidity Inline Assembly Example 6

pragma solidity ^0.4.0;

contract Cont {
    function func(uint a) returns (uint b) {
        assembly {
            let c := add(a, 1)
            mstore(0x80, c)
            {
                let d := add(sload(c), 1)
                b := d
            } // d is "deallocated" here
            b := add(b, c)
        } // c is "deallocated" here
    }
}