import java.io.InputStream; import java.io.IOException; import java.io.PrintWriter; import java.util.ArrayDeque; import java.util.ArrayList; import java.util.Arrays; import java.util.BitSet; import java.util.Comparator; import java.util.Collections; import java.util.Deque; import java.util.HashMap; import java.util.HashSet; import java.util.InputMismatchException; import java.util.Map; import java.util.NoSuchElementException; import java.util.PriorityQueue; import java.util.TreeMap; import java.util.TreeSet; import java.math.BigDecimal; import java.math.BigInteger; public class Main{ static PrintWriter out; static InputReader ir; static final int INF=Integer.MAX_VALUE; static final long LINF=Long.MAX_VALUE; static void solve(){ int c=ir.nextInt(); int n=ir.nextInt(); int[] x=ir.nextIntArray(n); int[] dp=new int[c+1]; Arrays.fill(dp,INF); dp[0]=0; for(int i=0;i=0;j--){ if(dp[j]!=INF) dp[j+x[i]]=Math.min(dp[j+x[i]],dp[j]+1); } } out.println(dp[c]==INF?-1:dp[c]); } public static void main(String[] args) throws Exception{ ir=new InputReader(System.in); out=new PrintWriter(System.out); solve(); out.flush(); } static class InputReader { private InputStream in; private byte[] buffer=new byte[1024]; private int curbuf; private int lenbuf; public InputReader(InputStream in) {this.in=in; this.curbuf=this.lenbuf=0;} public boolean hasNextByte() { if(curbuf>=lenbuf){ curbuf= 0; try{ lenbuf=in.read(buffer); }catch(IOException e) { throw new InputMismatchException(); } if(lenbuf<=0) return false; } return true; } private int readByte(){if(hasNextByte()) return buffer[curbuf++]; else return -1;} private boolean isSpaceChar(int c){return !(c>=33&&c<=126);} private void skip(){while(hasNextByte()&&isSpaceChar(buffer[curbuf])) curbuf++;} public boolean hasNext(){skip(); return hasNextByte();} public String next(){ if(!hasNext()) throw new NoSuchElementException(); StringBuilder sb=new StringBuilder(); int b=readByte(); while(!isSpaceChar(b)){ sb.appendCodePoint(b); b=readByte(); } return sb.toString(); } public int nextInt() { if(!hasNext()) throw new NoSuchElementException(); int c=readByte(); while (isSpaceChar(c)) c=readByte(); boolean minus=false; if (c=='-') { minus=true; c=readByte(); } int res=0; do{ if(c<'0'||c>'9') throw new InputMismatchException(); res=res*10+c-'0'; c=readByte(); }while(!isSpaceChar(c)); return (minus)?-res:res; } public long nextLong() { if(!hasNext()) throw new NoSuchElementException(); int c=readByte(); while (isSpaceChar(c)) c=readByte(); boolean minus=false; if (c=='-') { minus=true; c=readByte(); } long res = 0; do{ if(c<'0'||c>'9') throw new InputMismatchException(); res=res*10+c-'0'; c=readByte(); }while(!isSpaceChar(c)); return (minus)?-res:res; } public double nextDouble(){return Double.parseDouble(next());} public BigInteger nextBigInteger(){return new BigInteger(next());} public BigDecimal nextBigDecimal(){return new BigDecimal(next());} public int[] nextIntArray(int n){ int[] a=new int[n]; for(int i=0;i