#include <stdio.h>

int main() {
    int x = 0;

    int K;
    scanf("%d", &K);
    int A, B;
    scanf("%d %d", &A, &B);

    while(A <= B) {
        if (A % K == 0) {
            printf("OK\n");
            return 0;
        }
        A++;
    }
    
    printf("NG\n");
    return 0;
}