foo.cc: In function 'int main()':
foo.cc:17:10: error: 'i' was not declared in this scope
     for (i = 0; i < m; i++) {
          ^
foo.cc:18:10: error: 'a' was not declared in this scope
   cin >> a;
          ^
foo.cc:19:5: error: 'nums' was not declared in this scope
   ++nums[a];
     ^~~~
foo.cc:19:5: note: suggested alternative: 'puts'
   ++nums[a];
     ^~~~
     puts
foo.cc:21:7: error: 'i' was not declared in this scope
  for (i = 0; i < 1000; i++) {
       ^
foo.cc:22:10: error: 'nums' was not declared in this scope
   while (nums[i]--) {
          ^~~~
foo.cc:22:10: note: suggested alternative: 'puts'
   while (nums[i]--) {
          ^~~~
          puts
foo.cc:12:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&n,&m);
     ~~~~~^~~~~~~~~~~~~~
foo.cc:14:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&vn[i].id,&vn[i].num);
         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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