getting runtime error on testcase 11

Exit code is -1073741819

here is my code:

include

include<string.h>

include

using namespace std; int main() { string lame=""; string a,b="",c=""; int i,j,n; getline(cin,a);

for(i=0;i<a.length();i++)
 b[i]=a[i];
 sort(a.begin(),a.end());j=0;

for(i=0;i<a.length();i++)
{
    if(b[i]!=a[j])
    {
           lame.push_back(b[i]);

    }
    else
    {
       c.push_back(a[j]);
       j++;
    }

}
if(lame.length()!=0)
{
    reverse(lame.begin(),lame.end());
c=c+lame;
}
cout<<c<<endl;
return 0;

}