package contest191018; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.ArrayList; import java.util.Arrays; import java.util.InputMismatchException; import java.util.List; public class C { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(); char[] s = ns(n); // 3 7 // 11 59 19 // 991 9551 boolean[] unused = new boolean[n]; int ans = 0; LST lst = new LST(n+1); for(int i = n-1;i >= 0;i--) { if(s[i] == '9') { lst.set(i); }else if(s[i] == '5') { int ne = lst.next(i); if(ne != -1) { lst.unset(ne); ans++; }else { unused[i] = true; } } } int one = 0; for(int i = n-1;i >= 0;i--) { if(s[i] == '1') { int ne = lst.next(i); if(ne != -1) { lst.unset(ne); ans++; }else { one++; unused[i] = true; } } } for(int i = 0;i < n;i++) { if(lst.get(i)) { unused[i] = true; } } int par = -1; for(int i = 0;i < n;i++) { if(s[i] == '1' && unused[i]) { if(par == -1) { par = i; }else { unused[par] = false; unused[i] = false; par = -1; ans++; } } } out: for(int i = n-1;i >= 0;i--) { if(s[i] == '1' && unused[i]) { for(int j = i;j >= 0;j--) { if(s[j] == '5' && unused[j]) { for(int k = j-1;k >= 0;k--) { if(s[k] == '5' && unused[k]) { for(int l = k-1;l >= 0;l--) { if(s[l] == '9' && unused[l]) { unused[i] = unused[j] = unused[k] = unused[l] = false; ans++; break out; } } break out; } } break out; } } break out; } } out: for(int i = n-1;i >= 0;i--) { if(s[i] == '1' && unused[i]) { for(int j = i;j >= 0;j--) { if(s[j] == '9' && unused[j]) { for(int k = j-1;k >= 0;k--) { if(s[k] == '9' && unused[k]) { unused[i] = unused[j] = unused[k] = false; ans++; break out; } } break out; } } break out; } } for(char c : s) { if(c == '3' || c == '7') { ans++; } } out.println(ans); } public static class LST { public long[][] set; public int n; // public int size; public LST(int n) { this.n = n; int d = 1; for(int m = n;m > 1;m>>>=6, d++); set = new long[d][]; for(int i = 0, m = n>>>6;i < d;i++, m>>>=6){ set[i] = new long[m+1]; } // size = 0; } // [0,r) public LST setRange(int r) { for(int i = 0;i < set.length;i++, r=r+63>>>6){ for(int j = 0;j < r>>>6;j++){ set[i][j] = -1L; } if((r&63) != 0)set[i][r>>>6] |= (1L<= 0){ for(int i = 0;i < set.length;i++, r=r+63>>>6){ for(int j = 0;j < r+63>>>6;j++){ set[i][j] = 0; } if((r&63) != 0)set[i][r>>>6] &= ~((1L<= 0 && pos < n){ // if(!get(pos))size++; for(int i = 0;i < set.length;i++, pos>>>=6){ set[i][pos>>>6] |= 1L<= 0 && pos < n){ // if(get(pos))size--; for(int i = 0;i < set.length && (i == 0 || set[i-1][pos] == 0L);i++, pos>>>=6){ set[i][pos>>>6] &= ~(1L<= 0 && pos < n && set[0][pos>>>6]<<~pos<0; } public LST toggle(int pos) { return get(pos) ? unset(pos) : set(pos); } public int prev(int pos) { for(int i = 0;i < set.length && pos >= 0;i++, pos>>>=6, pos--){ int pre = prev(set[i][pos>>>6], pos&63); if(pre != -1){ pos = pos>>>6<<6|pre; while(i > 0)pos = pos<<6|63-Long.numberOfLeadingZeros(set[--i][pos]); return pos; } } return -1; } public int next(int pos) { for(int i = 0;i < set.length && pos>>>6 < set[i].length;i++, pos>>>=6, pos++){ int nex = next(set[i][pos>>>6], pos&63); if(nex != -1){ pos = pos>>>6<<6|nex; while(i > 0)pos = pos<<6|Long.numberOfTrailingZeros(set[--i][pos]); return pos; } } return -1; } private static int prev(long set, int n) { long h = set<<~n; if(h == 0L)return -1; return -Long.numberOfLeadingZeros(h)+n; } private static int next(long set, int n) { long h = set>>>n; if(h == 0L)return -1; return Long.numberOfTrailingZeros(h)+n; } @Override public String toString() { List list = new ArrayList(); for(int pos = next(0);pos != -1;pos = next(pos+1)){ list.add(pos); } return list.toString(); } } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new C().run(); } private byte[] inbuf = new byte[1024]; public int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }