HDU 2057 A + B Again

#include<stdio.h>
long long z,x,y;
int main( )
{
    while( scanf( "%I64x%I64x",&x,&y ) != EOF )
    {
           z = x + y;
           if( z < 0 )
               printf( "-" ), z = -z;
           printf( "%I64X\n",z );
           }           
    return 0;    
}