foo.cc: In member function 'void Block::calcQueryAns()':
foo.cc:134:9: warning: unused variable 'v' [-Wunused-variable]
     int v = ele_values[p];
         ^
foo.cc:114:7: warning: unused variable 'N' [-Wunused-variable]
   int N = ele_values.size();
       ^
foo.cc: In function 'void solve()':
foo.cc:170:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d%d", &n, &w, &q, &opt);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:173:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", a + i);
   ~~~~~^~~~~~~~~~~~~
foo.cc:182:90: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d", &l, &r, &k), l ^= opt * lastans, r ^= opt * lastans, k ^= opt * lastans, --l;
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
foo.cc: In function 'int main()':
foo.cc:196:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   freopen("input.txt", "r", stdin);
   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:197:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   freopen("output.txt", "w", stdout);
   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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