"use strict";
function main(input) {
    var line = input.split("\n");
    let K = parseInt(line[0]);
    let line2 = line[1].split(" ");
    let A = parseInt(line2[0]);
    let B = parseInt(line2[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'));