def main():

    K = int(eval(input()))

    A, B = list(map(int, input().split()))



    for x in range(A, B + 1):

        if x % K == 0:

            print('OK')

            return

    print('NG')





if __name__ == '__main__':

    main()



# import sys

# input = sys.stdin.readline

# 

# sys.setrecursionlimit(10 ** 7)

# 

# (int(x)-1 for x in input().split())

# rstrip()

#

# def binary_search(*, ok, ng, func):

#     while abs(ok - ng) > 1:

#         mid = (ok + ng) // 2

#         if func(mid):

#             ok = mid

#         else:

#             ng = mid

#     return ok

def main():

    from math import floor



    K = int(eval(input()))

    A, B = list(map(int, input().split()))



    multiple = floor(B / K) * K  # B以下の最大のKの倍数

    cond = (A <= multiple)  # A以上なら範囲内にある



    print(('OK' if cond else 'NG'))





if __name__ == '__main__':

    main()

   
def main():
    K = int(eval(input()))
    A, B = list(map(int, input().split()))
    for x in range(A, B + 1):
        if x % K == 0:
            print("OK")
            return
    print("NG")


if __name__ == "__main__":
    main()
# import sys
# input = sys.stdin.readline
#
# sys.setrecursionlimit(10 ** 7)
#
# (int(x)-1 for x in input().split())
# rstrip()
#
# def binary_search(*, ok, ng, func):
#     while abs(ok - ng) > 1:
#         mid = (ok + ng) // 2
#         if func(mid):
#             ok = mid
#         else:
#             ng = mid
#     return ok

def main():
    from math import floor

    K = int(eval(input()))
    A, B = list(map(int, input().split()))
    multiple = floor(B / K) * K  # B以下の最大のKの倍数
    cond = A <= multiple  # A以上なら範囲内にある
    print(("OK" if cond else "NG"))


if __name__ == "__main__":
    main()

+    from math import floor + -    for x in range(A, B + 1): -        if x % K == 0: -            print("OK") -            return -    print("NG") +    multiple = floor(B / K) * K  # B以下の最大のKの倍数 +    cond = A <= multiple  # A以上なら範囲内にある +    print(("OK" if cond else "NG")) -# import sys -# input = sys.stdin.readline -# -# sys.setrecursionlimit(10 ** 7) -# -# (int(x)-1 for x in input().split()) -# rstrip() -# -# def binary_search(*, ok, ng, func): -#     while abs(ok - ng) > 1: -#         mid = (ok + ng) // 2 -#         if func(mid): -#             ok = mid -#         else: -#             ng = mid -#     return ok