6.11.1.cpp

#include<iostream>
#include<cctype>
using namespace std;

int main()
{
	char a;
	cin.get(a);
	while (a != '@')
	{
		if (isupper(a))
			cout << char(a + 32);
		else if (islower(a))
			cout << char(a - 32);
		else if (isdigit(a))
			cout << "";
		else if (isspace(a))
			cout << " ";
		else
			cout << a;
		cin.get(a);
	}
	return 0;
}