关于字符串大小写的转换

后面有错误提示的附件：没搞懂怎么出现错误了？
#include<stdio.h>
#include<string.h>
int main()
{
    char left[20], right[20];
    int num=0;

    while (1)
    {
        printf("输入转换大小写的方式：1 表示大写，2 表示小写，0 表示结束\n");
        scanf_s("%d", &num);
        if (num == 1)
        {
            printf("输入一个字符\n");
            scanf_s("%s",&right);
            strcpy_s(left,right);
            _strupr_s(left);
            printf("转换成大写字母的字符串为：%s\n", left);
        }
        else if (num == 2)
        {
            printf("输入一个字符：\n");
            scanf_s("%s", &right);
            strcpy_s(left, right);
            _strlwr_s(left);
            printf("转换成小写字母的字符串为：%s", left);
        }
        else  if (num==0)
        {
            break;
        }
        
    }
    getchar();
    getchar();
    return 0;
}