123

include <bits/stdc++.h>

using namespace std; string a; int s=0; int main(){

cin>>a;

for(int i=0;i<a.size();i++){
	if(a[i]=='I'){
		s++; 
	}else{
		s--;
	}
	if(s<0){
		cout<<"NO"<<endl;
		break;
	}
}
if(s>=0)	{
	cout<<"YES"<<endl; 
}
return 0;

}