foo.cc: In function 'int main()':
foo.cc:36:3: warning: 'a' is used uninitialized in this function [-Wuninitialized]
  a%=mod; 
  ~^~~~~
foo.cc:37:3: warning: 'b' is used uninitialized in this function [-Wuninitialized]
  b%=mod;
  ~^~~~~
foo.cc:38:3: warning: 'c' is used uninitialized in this function [-Wuninitialized]
  c%=mod;
  ~^~~~~
foo.cc:39:3: warning: 'd' is used uninitialized in this function [-Wuninitialized]
  d%=mod;
  ~^~~~~

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