运行不了，想知道哪里出错了

#include
using namespace std;
int main()
{
char a,b;
cin >> a,b;
if (a >= 65 && a <= 90, b >= 65 && b <= 90)
a = a + 32, b = b + 32;
else if (a >= 97 && a <= 122, b >= 97 && b <= 122)
a = a - 32, b = b - 32;
cout << a << endl;
cout << b << endl;
}