pragma solidity ^0.4.25;

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) {
        require(b > 0);
        uint256 c = a / b;
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;
        return c;
    }

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);
        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}

contract BaseToken {
    using SafeMath for uint256;

    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;
    uint256 public _totalLimit;

    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);

    function _transfer(address from, address to, uint value) internal {
        require(to != address(0));
        balanceOf[from] = balanceOf[from].sub(value);
        balanceOf[to] = balanceOf[to].add(value);
        emit Transfer(from, to, value);
    }

    function _mint(address account, uint256 value) internal {
        require(account != address(0));
        totalSupply = totalSupply.add(value);
        require(_totalLimit >= totalSupply);
        balanceOf[account] = balanceOf[account].add(value);
        emit Transfer(address(0), account, value);
    }

    function transfer(address to, uint256 value) public returns (bool) {
        _transfer(msg.sender, to, value);
        return true;
    }

    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
        _transfer(from, to, value);
        return true;
    }

    function approve(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));
        allowance[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        require(spender != address(0));
        allowance[msg.sender][spender] = allowance[msg.sender][spender].add(addedValue);
        emit Approval(msg.sender, spender, allowance[msg.sender][spender]);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        require(spender != address(0));
        allowance[msg.sender][spender] = allowance[msg.sender][spender].sub(subtractedValue);
        emit Approval(msg.sender, spender, allowance[msg.sender][spender]);
        return true;
    }
}

contract CustomToken is BaseToken {
    constructor() public {
        name = 'International data coin';
        symbol = 'IDC';
        decimals = 18;
        totalSupply = 5000000000000000000000000;
        _totalLimit = 100000000000000000000000000000000;
        balanceOf[0x305897E62C08D92DBFD38e8Dd5d7eea4495b8c08] = totalSupply;
        emit Transfer(address(0), 0x305897E62C08D92DBFD38e8Dd5d7eea4495b8c08, totalSupply);
    }
}