function platformUnfreeze() external{
        uint month = 12;
        
        assert(DRC.freezeOf(msg.sender) > 0 );
        assert(finishTime > 0);
        assert(msg.sender == platform);
        uint step = safeSub(block.timestamp, finishTime) / (3600*24*30);
        
        uint256 freeze  = DRC.freezeOf(msg.sender);
        uint256 unfreezeAmount = 0;
        
        uint256 per = tokensForPlatform / month;
        
        for(uint i = 0 ;i <= step && i < month;i++){
            if(unfroze[i][msg.sender] == false){
                unfreezeAmount += per;
            }
        }
        
        require(unfreezeAmount > 0 );
        require(unfreezeAmount <= freeze);

        DRC.unfreeze(msg.sender,unfreezeAmount);
        for(uint j = 0; j <= step && i < month; j++){
            unfroze[j][msg.sender] = true;
        }
    }