import std.stdio, std.conv, std.string, std.algorithm,
       std.math, std.array, std.container, std.typecons;

long mod = 1000000007;

long modinv(long a) {
  long b=mod, u=1, v=0;
  while(b>0) {
    long t=a/b;
    a -= t*b; swap(a,b);
    u -= t*v; swap(u,v);
  }
  u %= mod;
  if(u<0) u+=mod;
  return u;
}

bool solve() {
  int k, a, b;
  k = readln.chomp.to!int;
  readf("%d %d\n", &a, &b);
  int l=k;
  while(l<=b) {
    if(a<=l && l<=b) return true;
    l += k;
  }
  return false;
}

void main() {
  if(solve) writeln("OK");
  else writeln("NG");
}
