import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken().to!int; }
long readLong() { return readToken().to!long; }
real readReal() { return readToken().to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


int N;
long[] A, B;

void main() {
  try {
    for (; ; ) {
      N = readInt();
      A = new long[N];
      B = new long[N];
      foreach (i; 0 .. N) {
        A[i] = readLong();
      }
      foreach (i; 0 .. N) {
        B[i] = readLong();
      }
      
      int needCnt;
      long need;
      long[] xs;
      foreach (i; 0 .. N) {
        if (A[i] < B[i]) {
          ++needCnt;
          need += (B[i] - A[i]);
        } else if (A[i] > B[i]) {
          xs ~= (A[i] - B[i]);
        }
      }
      xs.sort!((a, b) => (a > b));
      debug {
        writefln("need = %s", need);
        writefln("xs = %s", xs);
      }
      
      auto xsSum = new long[xs.length + 1];
      foreach (j; 0 .. xs.length) {
        xsSum[j + 1] = xsSum[j] + xs[j];
      }
      
      int ans = -1;
      foreach (j; 0 .. xs.length + 1) {
        if (need <= xsSum[j]) {
          ans = needCnt + j;
          break;
        }
      }
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}
