func: function mintTokensToEralyInvestors() onlyOwner {
      require(!earlyInvestorsMintedTokens);
      for(uint i  = 0; i < presale.totalInvestors(); i++) {
        address investorAddress = presale.investors(i);
        uint invested = presale.balanceOf(investorAddress);
        uint tokens = invested.mul(1 ether).div(price);
        uint bonusTokens = tokens.mul(earlyInvestorsBonus).div(percentRate);
        uint tokensWithBonus = tokens.add(bonusTokens);
        token.mint(this, tokensWithBonus);
        token.transfer(investorAddress, tokensWithBonus);
      }
      earlyInvestorsMintedTokens = true;
    }