为什么C语言报错写入位置时发生访问冲突？

在复习C语言的时候写了很简单的一个结构，代码如下：
#include
#include
struct student
{
char name[20];
int chinese;
int math;
double average;
};
void main()
{
student st[3];
int i,n;
printf("请输入学生个数\n");
scanf_s("%d", &n);
printf("请输入学生的姓名 语文成绩 数学成绩\n");
for (i = 0; i < n; i++)
{
scanf_s("%s %d %d", st[i].name, &st[i].chinese, &st[i].math);
st[i].average = (st[i].chinese + st[i].math ) / 2.0;
}
for (i = 0; i < n; i++)
printf("%s 平均成绩为：%f\n", st[i].name, st[i].average);
system("pause");
}
求问各位大佬调试的时候为什么会报错 “0x008C0B5C (ucrtbased.dll)处(位于 ConsoleApplication1.exe 中)引发的异常: 0xC0000005: 写入位置 0x3C900000 时发生访问冲突。”

//将输入部分修改一下：
for (i = 0; i < n; i++)
{
scanf_s("%s", st[i].name, 20);
scanf_s("%d %d", &st[i].chinese, &st[i].math);
st[i].average = (st[i].chinese + st[i].math) / 2.0;

}

//scanf_s在读入字符串的时候要加入size大小

 scanf("%s %d %d",st[i].name, &st[i].chinese, &st[i].math);

#include <stdio.h>

void main( void )
{
   int   i, result;
   float fp;
   char  c, s[81];
   wchar_t wc, ws[81];

   printf( "\n\nEnter an int, a float, two chars and two strings\n");

   result = scanf( "%d %f %c %C %s %S", &i, &fp, &c, &wc, s, ws );
   printf( "\nThe number of fields input is %d\n", result );
   printf( "The contents are: %d %f %c %C %s %S\n", i, fp, c, wc, s, ws);

   wprintf( L"\n\nEnter an int, a float, two chars and two strings\n");

   result = wscanf( L"%d %f %hc %lc %S %ls", &i, &fp, &c, &wc, s, ws );
   wprintf( L"\nThe number of fields input is %d\n", result );
   wprintf( L"The contents are: %d %f %C %c %hs %s\n", i, fp, c, wc, s, ws);
}

 #include <stdio.h>

int main( void )
{
   int      i,
            result;
   float    fp;
   char     c,
            s[81];
   wchar_t  wc,
            ws[81];

   result = scanf_s( "%d %f %c %C %s %S", &i, &fp, &c, 1,
                     &wc, 1, s, 80, ws, 80 );
   printf( "The number of fields input is %d\n", result );
   printf( "The contents are: %d %f %c %C %s %S\n", i, fp, c,
           wc, s, ws);
   result = wscanf_s( L"%d %f %hc %lc %S %ls", &i, &fp, &c, 2,
                      &wc, 1, s, 80, ws, 80 );
   wprintf( L"The number of fields input is %d\n", result );
   wprintf( L"The contents are: %d %f %C %c %hs %s\n", i, fp,
            c, wc, s, ws);
}

canf_s("%s %d %d", st[i].name, &st[i].chinese, &st[i].math);
st[i].name前没有加取地址符号