include <bits/stdc++.h>

using namespace std;

int main() {

//freopen(".in", "r", stdin);
//freopen(".out", "w", stdout);
stack<char>a;
string d;
int b, c = 0;
getline(cin, d);
for (int i = 0; i < d.size(); i++) {
	if (d[i] == 'O') {
		if (a.empty()) {
			cout << "NO";
			return 0;
		}
		a.pop();
	}
	if (d[i] == 'I') {
		a.push(c);
	}
}
cout << "YES";
return 0;

}