"use strict"
function main(arg) {
    let K = Number(arg.trim().split("\n")[0])
    let tmp = arg.trim().split("\n")[1].split(" ").map(Number)
    let A = tmp[0]
    let B = tmp[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'));