foo.cc: In function 'int M(int, int)':
foo.cc:10:11: warning: value computed is not used [-Wunused-value]
   M(a,n-1)*a;
   ~~~~~~~~^~
foo.cc:20:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^
foo.cc: In function 'int main()':
foo.cc:20:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^
foo.cc:7:7: note: 'c' was declared here
  long c;
       ^

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