interface IERC20 {
    /**
     * Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * Returns the amount of tokens owned by 'account'.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * Moves 'amount' tokens from the caller's account to 'recipient'.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a 'Transfer' event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * Returns the remaining number of tokens that 'spender' will be
     * allowed to spend on behalf of 'owner' through 'transferFrom'. This is
     * zero by default.
     *
     * This value changes when 'approve' or 'transferFrom' are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * Sets 'amount' as the allowance of 'spender' over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * > Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an 'Approval' event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * Moves 'amount' tokens from 'sender' to 'recipient' using the
     * allowance mechanism. 'amount' is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a 'Transfer' event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * Emitted when 'value' tokens are moved from one account ('from') to
     * another ('to').
     *
     * Note that 'value' may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * Emitted when the allowance of a 'spender' for an 'owner' is set by
     * a call to 'approve'. 'value' is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}
/**
 * Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see 'ERC20Detailed'.
 */
function balanceOf(address account) external view returns (uint256);

/**
 * Returns the amount of tokens owned by 'account'.
 */