/// Frail the skin is dry and pale
#pragma GCC optimize("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("avx,avx2,fma")
using namespace std;

#include "bits/stdc++.h"
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>

using namespace __gnu_pbds;
using namespace __gnu_cxx;

using ll = long long;
using ii = pair<int, int>;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define pb push_back
#define F first
#define S second
#define f(i, a, b)  for(int i = a; i < b; i++)
#define all(a)  a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define sz(x) (int)(x).size()
#define mp make_pair

const int N = 5e4 + 5, LG = 18, MOD = 31607;
const double PI = acos(-1);

void doWork() {

    int n;  cin >> n;
    string s; cin >> s;

    set<int> st[2];
    for(int i = 0; i < n; i++) {
        st[s[i]-'0'].insert(i);
    }

    int ptr = 0;
    int f1 = s[0] - '0';
    int f2 = s.back() - '0';
    int cnt = 0;
    while(s[ptr]-'0' != f1 || st[f1].size() != 1) {
        st[s[ptr]-'0'].erase(ptr);
        cnt += 1;
        ptr++;
    }
     ptr = n - 1;
    while(s[ptr]-'0' != f2 || st[f2].size() != 1) {
        st[s[ptr]-'0'].erase(ptr);
        cnt += 1;
        ptr--;
    }

    cout << cnt << '\n';


}
int32_t main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0);
    cin.tie(0);
#endif // ONLINE_JUDGE
    int t = 1;
//    cin >> t;
    while (t--) {
        doWork();
    }


    return 0;
}