class Solution {

public:

    string addBinary(string a, string b) {

        string longer=a.length()>b.length() ? a:b;

        string shorter=a.length()>b.length() ? b:a;

        int add=;

        int j=longer.length()-;

        for(int i=shorter.length()-;i>=;--i,--j){

            if(shorter[i]-''+longer[j]-''+add>){

                longer[j]=''+(shorter[i]-''+longer[j]-''+add)%;

                add=;

            }else{

                longer[j]=''+(shorter[i]-''+longer[j]-''+add)%;

                add=;

            }

        }

        while(j>=){

            if(longer[j]-''+add>){

                longer[j]='';

                add=;

            }else{

                longer[j]=longer[j]+add;

                add=;

            }

            --j;

        }

        if(add)

            longer.insert(,,'');

        return longer;

    }

};