pepecoin.sol

contract PepeCoin{
    uint dec = 10**18;
    mapping(address => uint) balances;

    function buy(uint tokens) public payable{
        uint required_wei = (tokens / 10) * dec;
        if (msg.value >= required_wei){
            balances[msg.sender] += tokens;
        }else{
            revert();
        }
    }

    function sell(uint tokens) public payable{
        uint wei_to_send = ( tokens / 10 ) * dec;
        if (balances[msg.sender] >= tokens){
            msg.sender.transfer(wei_to_send);
            balances[msg.sender] -= wei_to_send*10;
        }
    }

    function transfer(address to, uint tokens) public {
        require(balances[msg.sender] >= tokens);
        balances[msg.sender] -= tokens;
        balances[to] += tokens;
    }
}

https://gist.github.com/feliam/f43c87c5425a47e326da2a0f8c61230b