原题传送门

$my$ $code$

#include<cstdio>
char key;
int main()
{
	while(scanf("%c",&key)&&key!='\n'&&key!='\r')
	{
		if(key!='\n'&&key!='\r')
		{
			if(key>='A'&&key<='Z') key+=32;
			else if(key>='a'&&key<='z') key-=32;
			printf("%c",key);
		}
	}
	printf("\n");
	return 0;
}

是OLE