const main = (input) => {
    input = input.split('\n');
    const K = input[0];
    const tmp = input[1].split(' ');
    const A = parseInt(tmp[0]);
    const B = parseInt(tmp[1]);

    for (let i = A; i <= B; i++) {
        if (i % K === 0) {
            console.log('OK');
            return;
        }
    }

    console.log('NG');
};

// 標準入力
main(require('fs').readFileSync('/dev/stdin', 'utf8'));