#include<bits/stdc++.h>
using namespace std;
int main(){
	char x,z;
	long long int y,w;
	cin>>x>>y>>z>>w;
	if(x==z && x>='a' && x<='z' && z>='a' && z<='z'){
		cout<<"valid"<<endl;
		if(y<=w){
			cout<<w-y+1<<endl;
		}else{
			cout<<y-w+1<<endl;
		}
	}else{
		cout<<"Invalid"<<endl;
		cout<<-1<<endl;
	}
}