#include <iostream>
using namespace std;
string a;
int main() {
    cin >> a;
    if (a[0] >= 'a' && a[0] <= 'z') a[0] ^= 32;
    for (unsigned i = 1; i < a.size(); i++)
    	if (a[i] >= 'A' && a[i] <= 'Z')
    		a[i] ^= 32;
    cout << a;
}

提交上去就给我干了个 $\textcolor{black}{Unknown \ Error}$