为什么要输入2次数字才可以？为什么键盘输入会自动呈现一个数字啊

Question

#include <stdio.h>

int sum()
{
int num = 0;
int result = 0;

printf("请输入一个数字：%d\n", &num);
scanf("%d\n", &num);

do
{
    result += num;
}while(num-- > 0);

printf("从1加到的数字的和为：%d\n", result);

return result;

}

int main()
{

 sum();

return 0;

}

Answer 1

#include <stdio.h>
int sum()
{
int num = 0;
int result = 0;
printf("请输入一个数字：\n");
scanf("%d",&num);
do
{
    result += num;
}while(num-- > 0);
printf("从1加到的数字的和为：%d\n", result);
return result;
}
int main()
{
  sum(); 
  return 0;
}