"use strict";
    
const main = arg => {
    arg = arg.trim().split("\n");
    const K = parseInt(arg[0].split(" ")[0]);
    const A = parseInt(arg[1].split(" ")[0]);
    const B = parseInt(arg[1].split(" ")[1]);
    
    for(let i=A; i<=B; i++) {
        if(i % K === 0) {
            console.log("OK");
            return;
        }
    }
    
    console.log("NG");
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));