/in/foo.cc: In function 'int main()':
/in/foo.cc:12:6: error: 'i' was not declared in this scope
  for(i=0;i<b;i++) b+=a[i]-48;
      ^
/in/foo.cc:7:10: warning: unused variable 'c' [-Wunused-variable]
  int b=0,c=0;
          ^