/** * code generated by JHelper * More info: https://github.com/AlexeyDmitriev/JHelper * @author */ #include #include #ifndef SOLUTION_COMMON_H #include using namespace std; using ll = long long; using PI = pair; template using V = vector; using VI = V; #define _1 first #define _2 second #ifdef MY_DEBUG # define DEBUG(x) x #else # define DEBUG(x) #endif template inline void debug(T &A) { DEBUG( for (const auto &a : A) { cerr << a << " "; } cerr << '\n'; ) } template inline void debug_with_format(T &A, Func f) { DEBUG( for (const auto &a : A) { cerr << f(a) << " "; } cerr << '\n'; ) } template inline void debug_dim2(T &A) { DEBUG( for (const auto &as : A) { debug(as); } ) } template inline void debug(const char *format, Args const &... args) { DEBUG( fprintf(stderr, format, args ...); cerr << '\n'; ) } template string format(const string &fmt, Args ... args) { size_t len = snprintf(nullptr, 0, fmt.c_str(), args ...); vector buf(len + 1); snprintf(&buf[0], len + 1, fmt.c_str(), args ...); return string(&buf[0], &buf[0] + len); } template string fmtP(pair a) { stringstream ss; ss << "(" << a._1 << "," << a._2 << ")"; return ss.str(); } #define SOLUTION_COMMON_H #endif //SOLUTION_COMMON_H const int MOD = 1000000007; class C { public: void solve(std::istream& in, std::ostream& out) { int n; string s; in >> n >> s; VI l(n), r(n); for (int i = 0; i < n; ++i) { if (i > 0) l[i] = i - 1; if (i < n - 1) r[i] = i + 1; } l[0] = -1; r[n - 1] = -1; int ans = 0; int i = 0; while(i != -1) { if (s[i] == '3' || s[i] == '5' || s[i] == '7') { ans++; int R = r[i]; int L = l[i]; debug("* %d %d %d", i, R, L); if (R != -1) l[R] = L; if (L != -1) r[L] = R; i = L != -1 ? L : R; continue; } // 11 | 19 if ((s[i] == '1' && l[i] != -1 && s[l[i]] == '1') || (s[i] == '9' && l[i] != -1 && s[l[i]] == '1') ) { ans++; int R = r[i]; int L = l[l[i]]; debug("** %d %d %d", i, R, L); if (R != -1) l[R] = L; if (L != -1) r[L] = R; i = L != -1 ? L : R; continue; } i = r[i]; } out << ans; } }; int main() { C solver; std::istream& in(std::cin); std::ostream& out(std::cout); solver.solve(in, out); return 0; }