#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using ll = long long; using P = std::pair; #define rep(i, a, b) for (ll(i) = (a); i < (b); i++) #define all(i) i.begin(), i.end() #define debug(i) std::cerr << "debug " << i << std::endl template std::ostream& operator<<(std::ostream& os, std::pair pa) { return os << pa.first << " " << pa.second; } template std::ostream& operator<<(std::ostream& os, std::vector vec) { for (int i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " "); return os; } template inline bool chmax(T1& a,T2 b){return a inline bool chmin(T1& a,T2 b){return a>b && (a=b,true);} // const ll MOD = 998244353; const ll MOD = 1e9 + 7; ll pow_mod(ll a, ll b, ll mod=-1) { if ((a == 0)||(mod!=-1&&a%mod==0)) { return 0; } ll x = 1; while (b > 0) { if (b & 1) { x = (mod!=-1)?(x * a) % mod:x*a; } a = (mod!=-1)?(a * a) % mod:a*a; b >>= 1; } return x; } int main() { std::cin.tie(0); std::ios::sync_with_stdio(false); ll n; std::cin>>n; std::string s; std::cin>>s; ll ans=0; bool used=false; rep(i,0,n){ if(s[i]=='3'||s[i]=='5'||s[i]=='7'){ ans++; }else if(s[i]=='9'){ if(used){ ans++; used=false; } }else{ if(used){ ans++; used=false; }else{ used=true; } } } std::cout<