#include <wchar.h>

wchar_t* wcsncat(wchar_t* restrict d, const wchar_t* restrict s, size_t n) {
  wchar_t* a = d;
  d += wcslen(d);
  while (n && *s)
    n--, *d++ = *s++;
  *d++ = 0;
  return a;
}