/in/foo.cc: In function 'void shell2()':
/in/foo.cc:31:9: error: 'j' was not declared in this scope
    stud[j + d].sc = temp;
         ^
/in/foo.cc: In function 'void shell1()':
/in/foo.cc:51:9: error: 'j' was not declared in this scope
    stud[j + d].id = temp;
         ^