include <bits/stdc++.h>

using namespace std;

define ll long long

int main() { ll a,b,c; cin>>a>>b>>c; if(a+b>c and a+c>b and b+c>a) { if(a==b and b==c) { cout<<"equilateral"<<endl; } else if(a==b or b==c or a==c) { cout<<"isosceles"<<endl; } else { cout<<"versatile"<<endl; } } else { cout<<"invalid"<<endl; } return 0; }