它写的A+B什么东西啊

https://aigcfun.com/

#include <stdio.h>
int main()
{
    int a, b;
    scanf("%!d(MISSING) %!d(MISSING)", &a, &b);
    printf("%!d(MISSING)\n", a + b);
    return 0;
}

这%!d(MISSING)什么东西啊