/in/foo.cc: In function 'int main()':
/in/foo.cc:48:22: warning: unused variable 'ans' [-Wunused-variable]
   int p[101] = { 0 },ans;
                      ^~~
/in/foo.cc:33:12: warning: unused variable 'k' [-Wunused-variable]
  int i, j, k;
            ^
/in/foo.cc: In function 'void add(int*, int)':
/in/foo.cc:28:5: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
  p[u]++;
     ^