// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface ERC20 {
  function totalSupply() external view returns (uint256);
  function balanceOf(address who) external view returns (uint256);
  function allowance(address owner, address spender) external view returns (uint256);
  function transfer(address to, uint256 value) external returns (bool);
  function approve(address spender, uint256 value) external returns (bool);
  function transferFrom(address from, address to, uint256 value) external returns (bool);

  event Transfer(address indexed from, address indexed to, uint256 value);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract USDT is ERC20 {
  using SafeMath for uint256;

  mapping (address => uint256) private balances;
  mapping (address => mapping (address => uint256)) private allowed;
  string public constant name  = "Tether USD";
  string public constant symbol = "USDT";
  uint8 public constant decimals = 18;
  address public owner;
  uint256 _totalSupply = 1000000000000000000000000000;

  constructor() {
    owner = 0x5253a74788F67416e9872B38bdEef8722EA8AF1f;
    balances[owner] = _totalSupply;
    emit Transfer(address(0), owner, _totalSupply);
  }

  function totalSupply() public view returns (uint256) {
    return _totalSupply;
  }

  function balanceOf(address player) public view returns (uint256) {
    return balances[player];
  }

  function allowance(address player, address spender) public view returns (uint256) {
    return allowed[player][spender];
  }


  function transfer(address to, uint256 value) public returns (bool) {
    require(value <= balances[msg.sender]);
    require(to != address(0));

    balances[msg.sender] = balances[msg.sender].sub(value);
    balances[to] = balances[to].add(value);

    emit Transfer(msg.sender, to, value);
    return true;
  }

  function approve(address spender, uint256 value) public returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = value;
    emit Approval(msg.sender, spender, value);
    return true;
  }

  function transferFrom(address from, address to, uint256 value) public returns (bool) {
    require(value <= balances[from]);
    require(value <= allowed[from][msg.sender]);
    require(to != address(0));
    
    balances[from] = balances[from].sub(value);
    balances[to] = balances[to].add(value);
    
    allowed[from][msg.sender] = allowed[from][msg.sender].sub(value);
    
    emit Transfer(from, to, value);
    return true;
  }

  function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = allowed[msg.sender][spender].add(addedValue);
    emit Approval(msg.sender, spender, allowed[msg.sender][spender]);
    return true;
  }

  function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = allowed[msg.sender][spender].sub(subtractedValue);
    emit Approval(msg.sender, spender, allowed[msg.sender][spender]);
    return true;
  }

  function transferOwnership(address newOwner) public {
    require(msg.sender == owner, "not owner");
    require(newOwner != address(0));
    owner = newOwner;
  }

	function renounceOwnership() public {
    require(msg.sender == owner, "not owner");
    owner = address(0);
  }

}

library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0) {
      return 0;
    }
    uint256 c = a * b;
    require(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a / b;
    return c;
  }

  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a);
    return c;
  }

  function ceil(uint256 a, uint256 m) internal pure returns (uint256) {
    uint256 c = add(a,m);
    uint256 d = sub(c,1);
    return mul(div(d,m),m);
  }
}