#include <iostream>
using namespace std;


int main() {
//     freopen("input.txt", "r", stdin);
// 	freopen("output.txt", "w", stdout);
	
	char a[100000];
	int n;
	cin >> n;
	for (int i = 0; i < n; ++i)
	{
		cin >> a[i];
	}
	int x = a[0], y = a[n-1];
	int mn = 100000000;
	for (int i = 0; i < n; ++i)
	{
		if (a[i] == x)
		{
			for (int j = i; j < n; ++j)
			{
				// cout <<a[i] << " " <<  j << " "  << (j-i)+1 << endl;
				if (a[j] == y)
				{
					mn = min(mn, ((j-i)+1));
					// cout << mn << endl;
					break;
				}
			}
		}
	}
	cout << n-mn;
}