#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;
}