foo.cc: In function ‘int feb(int)’:
foo.cc:4:5: error: lvalue required as left operand of assignment
    4 |  feb(1)=1;
      |  ~~~^~~
foo.cc:5:5: error: lvalue required as left operand of assignment
    5 |  feb(2)=1;
      |  ~~~^~~
foo.cc: In function ‘int main()’:
foo.cc:13:19: error: ‘sum’ was not declared in this scope
   13 |         if(i>=k1) sum+=feb(i);
      |                   ^~~
foo.cc:15:15: error: ‘sum’ was not declared in this scope
   15 |         cout<<sum;
      |               ^~~