foo.cc: In function 'int main()':
foo.cc:9:17: error: 'n' was not declared in this scope
  for(int i=1;i<=n;i++){
                 ^
foo.cc:10:22: error: 'm' was not declared in this scope
   int ans=i*(n-2*i)*(m-2*i);
                      ^
foo.cc:7:6: warning: unused variable 'sum' [-Wunused-variable]
  int sum=0;
      ^~~

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