foo.c: In function 'main':
foo.c:6:12: error: lvalue required as left operand of assignment
    6 |         a+b=c;
      |            ^
foo.c:7:12: error: lvalue required as left operand of assignment
    7 |         a-b=d;
      |            ^

[Hydro](https://hydro.ac)提供评测服务