/in/foo.cc: In function 'int main()':
/in/foo.cc:6:13: warning: 'c' is used uninitialized [-Wuninitialized]
    6 |         int r4=c%4;
      |             ^~
/in/foo.cc:5:17: note: 'c' was declared here
    5 |         int a,b,c;
      |                 ^