include<stdio.h>

int main()
{
    int n, a, b;
    int flag = 0;
    
    scanf("%d", &n);

    scanf("%d %d", &a, &b);
    
    for(int i = a ; i <= b; i++){
        if(i % n == 0){
            flag = 1;
        }
    }
    if(flag == 1){
        printf("OK\n");
    }else{
        printf("NG\n");
    }
}