示例代码

#include<bits/stdc++.h>
using namespace std;

int main()
{
	char x,z;
	long long y,w;
	cin>>x>>y>>z>>w;
	if(x==z&&'a'<=x<='z')
	{
		cout<<"valid\n"<<abs(w-y)+1;
	}
	else
	{
		cout<<"Invalid\n-1";
	}
	return 0;
}