const input = require('fs').readFileSync('/dev/stdin', 'utf8');
const lines = input.split('\n');
const K = +lines[0];
const line2nd = lines[1].split(' ');
const A = +line2nd[0];
const B = +line2nd[1];

// console.log(`K=${K} A=${A} B=${B}`);

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

if (!isOK) {
    console.log('NG');
}
