// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

contract MyToken {

    string public name = "MyToken";

    string public symbol = "MTK";

    uint8 public decimals = 18;

    uint256 public totalSupply;

    mapping(address => uint256) public balanceOf;

    mapping(address => mapping(address => uint256)) public allowance;

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);

    constructor(uint256 initialSupply) {

        totalSupply = initialSupply * 10**uint256(decimals);

        balanceOf[msg.sender] = totalSupply;

    }

    function transfer(address _to, uint256 _value) public returns (bool success) {

        require(_to != address(0), "Invalid address");

        require(balanceOf[msg.sender] >= _value, "Insufficient balance");

        balanceOf[msg.sender] -= _value;

        balanceOf[_to] += _value;

        emit Transfer(msg.sender, _to, _value);

        return true;

    }

    function approve(address _spender, uint256 _value) public returns (bool success) {

        allowance[msg.sender][_spender] = _value;

        emit Approval(msg.sender, _spender, _value);

        return true;

    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {

        require(_from != address(0), "Invalid address");

        require(_to != address(0), "Invalid address");

        require(balanceOf[_from] >= _value, "Insufficient balance");

        require(allowance[_from][msg.sender] >= _value, "Allowance exceeded");

        balanceOf[_from] -= _value;

        balanceOf[_to] += _value;

        allowance[_from][msg.sender] -= _value;

        emit Transfer(_from, _to, _value);

        return true;

    }

}