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