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

int main() {
	int n;
	cin>>n;
	
	vector<int> numbers(n);
	
	for(auto& number: numbers){
		cin>>number;
	}
	
	int distance = INT_MIN;
	
	for(int i=0; i<n; i++){
		for(int j=i+1; j<n; j++){
			if(numbers[i] == numbers[j])distance = max(distance, j - i);
		}
	}
	
	if(distance == INT_MIN) distance = 0;
	
	cout<<distance;
	
	return 0;
}