pragma solidity ^0.4.24;

contract Concatenation {
     function concatenate(string _first, string _second, string _separator) public view returns (string) {}
}

contract StringUtil {
    
    address concatenationContractAddress = 0x0dcd2f752394c41875e259e00bb44fd505297caf;
    Concatenation concatenation = Concatenation(concatenationContractAddress);
    
    function concatenate(string _first, string _second, string _separator) public view returns (string){
        return concatenation.concatenate(_first, _second, _separator);
    }
    
}