#include <iostream>
using namespace std;
string strlower(string s) {
for (int i = 0; i < s.length(); i++) {
if (s[i] >= 'A' && s[i] <= 'Z')
s[i] = s[i] + 32;
}
return s;
}
int main() {
string str, ans = "";
while (cin >> str && str.length() > 4) {
for (int i = 0; i < str.length(); ++i)
if ((str[i] >= 'a' && str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z') || (str[i] >= '0' && str[i] <= '9' ) || (str[i] == ' ')) {
ans += strlower(str);
}
}
cout << ans;
return 0;
}
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