#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a,b,c;
	cin>>a>>b>>c;
	if(a+b>c&&b+c>a&&a+c>b){
	cout<<"OK"<<endl;	
		
	}else{
		cout<<"NO"<<endl;	
	}
	return 0;
}

/**************************************************************
	Problem: 1045
	User: ct001
	Language: C++
	Result: Wrong Answer
****************************************************************/