"use strict";
const p = (s) => console.log(s);
// let a,b,c,d;
// [a,b,c,d] = input[0].trim().split(" ").map(i => parseInt(i));

function main(input) {
  const K = input[0].split(" ")[0];
  const A = input[1].split(" ")[0];
  const B = input[1].split(" ")[1];
  let flag = false;

  for (let i = A; i <= B; i++) {
    if (Math.floor(i % K) === 0) {
      p("OK");
      flag = true;
      break;
    }
  }
  if (!flag) {
    p("NO");
  }
}
main(require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n"));
