#include <iostream>

using namespace std;

int Len(string &str1, string &str2)

{

int len1 = str1.size();

int len2 = str2.size();

if (len1 < len2)

{

for (int i = 0 ; i < len2 - len1 ; i++)

str1 = '0' + str1;

return len2;

}

else if (len1 > len2)

{

for (int i = 0 ; i < len1 - len2 ; i++)

str2 = '0' + str2;

}

return len1;

}

string add( string a, string b )

{

string result;

int len = Len(a, b);

int carry = 0;

for (int i = len-1 ; i >= 0 ; i--)

{

int aBit = a.at(i) - '0';

int bBit = b.at(i) - '0';

int sum = (aBit ^ bBit ^ carry)+'0';

result = (char)sum + result;

carry = (aBit & bBit) | (bBit & carry) | (aBit & carry);

}

if (carry)

result = '1' + result;

return result;

}

int main()

{

string str1,str2;

cout<<"Enter the string 1 :";

cin>>str1;

cout<<"Enter the string 2 :";

cin>>str2;

cout << "Sum is " << add(str1, str2);

return 0;

}