#include <iostream>
#include <algorithm>
#include <iterator>
#include <math.h>
#include <vector>
#include <set>
using namespace std;
int main() {
	int n;
	string s;
	cin >> n >> s;
	char x = s[0];
	char y = s[n - 1];
	int j = n - 1, c1 = 0, c2 = 0;
	bool f = 0;
	for (int i = 0; i < j; i++) {
		if (s[i] == x && i < j) {
			c1 = i;
		}
		if (s[j] == y && i < j) {
			c2 = j;
		}
		if (s[i] == x && s[i + 1] == y) {
			f = 1;
			break;
		}
		if (s[j] == y && s[j - 1] == x) {
			f = 1;
			break;
		}
		j--;
	}
	if (!f)
		cout << (n - c2) + c1;
	else cout << n - 2;
	return 0;
}