pragma solidity ^0.6.0;

abstract contract TokenInterface {
    function allowance(address, address) public virtual returns (uint256);

    function balanceOf(address) public virtual returns (uint256);

    function approve(address, uint256) public virtual;

    function transfer(address, uint256) public virtual returns (bool);

    function transferFrom(address, address, uint256) public virtual returns (bool);

    function deposit() public virtual payable;

    function withdraw(uint256) public virtual;
}