#include <stdio.h>

int main(void){
    int k, a, b;
    int ret = 0;

    scanf("%d %d %d", &k, &a, &b);
    
    for(int i = a; i <= b; ++i){
        if((i % k) == 0){
            ret = 1;
            break;
        }
    }

    if(ret == 1) printf("OK\n");
    else printf("NG\n");

    return 0;
}