include <bits/stdc++.h>

using namespace std;

int main() { int a, b, c;

cin >> a >> b >> c;

if(a > b && b <= c)cout << ":)\n";
else if(a < b && b < c && c - b > b - a) cout << ":)\n";
else if(a > b && b > c && c - b > b - a) cout << ":)\n";
else if(a == b && b < c) cout << ":)\n";
else if(a == b && b == c) cout << ":(\n";
else cout << ":(\n";

return 0;

}