#include #define rep(i,a,b) for(int i=a;i=b;i--) #define fore(i,a) for(auto &i:a) #define all(x) (x).begin(),(x).end() //#pragma GCC optimize ("-O3") using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); } typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60; templatebool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; } templatebool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; } //--------------------------------------------------------------------------------------------------- /*---------------------------------------------------------------------------------------------------             ∧_∧       ∧_∧  (´<_` )  Welcome to My Coding Space!      ( ´_ゝ`) /  ⌒i @hamayanhamayan     /   \    | |     /   / ̄ ̄ ̄ ̄/  |   __(__ニつ/  _/ .| .|____      \/____/ (u ⊃ ---------------------------------------------------------------------------------------------------*/ int N; string S; //--------------------------------------------------------------------------------------------------- void _main() { cin >> N >> S; int ans = 0; int cnt1 = 0, cnt9 = 0; rep(i, 0, N) { if (S[i] == '1') { if (2 <= cnt9) { cnt9 -= 2; ans++; } else cnt1++; } else if (S[i] == '9') { if (0 < cnt1) { cnt1--; ans++; } else cnt9++; } else ans++; } ans += cnt1 / 2; cout << ans << endl; }