process.stdin.resume();
process.stdin.setEncoding('utf8');

var lines = []
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});

reader.on('line', (line) => {
  lines.push(line);
});

reader.on('close', () => {
 var k = Number(lines[0]);
 var ab = lines[1].split(' ');
 var ab = ab.map(function(str) { return Number(str)});
 var a = ab[0];
 var b = ab[1];
 var count = 0;
 for(i=a; i<=b; i++){
   if(i % k == 0){
     console.log("OK");
     count++;
     break;
   }
 }

 if(count==0){
   console.log('NG');
 }
});