#include<bits/stdc++.h>  
using namespace std;  
int main(){  
	char x,z;  
	long long y,w;  
	cin>>x>>y>>z>>w;  
	if(x==z){  
		cout<<"valid"<<endl;  
		if(y<=w)  cout<<w-y+1<<endl;  
		else cout<<y-w+1<<endl;  
	}  
	else	cout<<"Invalid"<<endl<<"-1"<<endl;  
	return 0;  
} 

90分哪里错了？