The following code is failing the test case 3, I have used linked-list to store the data in as a stack. Below is the code for reference, can you tell me where I am going wrong. Thank you.

#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>
#include<math.h>
#include<assert.h>

typedef unsigned long long _ull;
typedef unsigned int _uint;

typedef struct _link_list {
    _ull _number;
    struct _link_list*_next;
} _list;

void _makenode(_list**,_ull);
void _insertnode(_list**,_list*);

int main(int argc,const char*argv[]) {
    _ull _val;
    _list *_head,*_temp;
    _head = _temp = NULL;
    while(true) {
        fscanf(stdin,"%lld",&_val);
        assert(_val>=0);
        if(feof(stdin)) break;
        _makenode(&_head,_val);
    }
    while(_head) {
        _temp = _head;
        fprintf(stdout,"%0.4lf\n",sqrt(_head->_number));
        _head = (_head->_next);
        free(_temp);
    }
    return 0;
}

void _makenode(_list**_ptr,_ull _data) {
    _list*_node = malloc(sizeof(_list));
    (_node->_number) = _data;
    (_node->_next) = NULL;
    _insertnode(_ptr,_node);
}

void _insertnode(_list**_ptr,_list*_node) {
    if(!(*_ptr)) (*_ptr) = _node;
    else {
        (_node->_next) = (*_ptr);
        (*_ptr) = _node;
    }
}