#include <stdio.h>

int main(void){
    int k,a,b,c,ans=0,i;
    scanf("%d %d %d",&k,&a,&b);

    c = a/k;

    for(i=c;i*k<=b;i++){
        if(a <= k*i && k*i <= b) ans = 1; break;
    }

    if(ans == 1){
        printf("OK\n");
    }else{
        printf("NG\n");
    }

    return 0;
}