Binary Multiplication

#include<bits/stdc++.h>
using namespace std;
string toBinary(int n)
{
    string s;
    while(n)
    {
        s.push_back((n%2)+'0');
        n/=2;
    }
    reverse(s.begin(),s.end());
    return s;
}
string sum(string a, string b)
{
    reverse(a.begin(),a.end());
    reverse(b.begin(),b.end());
    while(a.size()!=b.size())
    {
        if(a.size()<b.size())
            a.push_back('0');
        else
            b.push_back(48);
    }

    int carry=0,temp;
    string ans="";
    for(int i=0; i<a.size(); i++)
    {
        temp=(a[i]-48)+(b[i]-48);
        temp+=carry;
        carry=0;
        ans.push_back((temp%2)+48);
        carry=((temp/2)%2);
    }
    //cout<<"carry = "<<carry<<endl;
    while(carry)
    {
        ans.push_back((carry%2)+48);
        carry/=2;
    }
    reverse(ans.begin(),ans.end());
    return ans;
}
void multiply(int x, int y)
{
    string a=toBinary(x);
    string b=toBinary(y);
    //cout<<a<<endl<<b<<endl;
    string val="0", ans="";
    for(int i=b.size()-1,k=0; i>=0; i--,k++)
    {
        val="";
        for(int j=0; j<a.size(); j++)
        {
            val+=((a[j]-48)&(b[i]-48))+48;
        }
        if(ans.empty())
            ans=val;
        else
        {
            for(x=0; x<k; x++)
                val+='0';
            ans=sum(ans,val);
        }
    }
    cout<<ans<<endl;
}

int main()
{
    long long a,b;
    //Enter First Number
    cin>>a;
    //Enter Second Number
    cin>>b;
    multiply(a,b);



}