/in/foo.cc: In function 'int main()':
/in/foo.cc:5:22: warning: 'n' is used uninitialized [-Wuninitialized]
    5 |         for(int i=1;i<=n;i++){
      |                     ~^~~
/in/foo.cc:4:13: note: 'n' was declared here
    4 |         int n,c,a=0,b=0;
      |             ^