#include <stdio.h>


int S,A,B;
int N[500][4];
int n;

char flag;

int judge(int J[])
{
	int i;
	if(flag==0)return 0;
	for(i=0;i<n;i++)
	{
		if(N[i][0]==J[0]&&N[i][1]==J[1]&&N[i][2]==J[2])return 0;
		if(J[2]==S/2&&J[0]==S/2){printf("%d\n",J[3]);flag=0; return 0;}
		if(J[1]==S/2&&J[0]==S/2){printf("%d\n",J[3]);flag=0; return 0;}
		if(J[2]==S/2&&J[1]==S/2){printf("%d\n",J[3]);flag=0; return 0;}
	}
	return 1;
}


int dao_a2b(int J[],int a, int b,int I[])
{
	int CA;
	int MID;
	int NONE;
	if(flag==0)return 0;
	if(a==b)return 0;
    if(I[a]==0)return 0;
	switch (b){
		case 0: CA=S; if(a==1)NONE=2; else NONE=1; break;
		case 1: CA=A; if(a==0)NONE=2; else NONE=0; break;
		case 2: CA=B; if(a==0)NONE=1; else NONE=0; break;
	}
    if(CA-I[b]==0)return 0;	
	MID=I[a]<CA-I[b]?I[a]:CA-I[b];
	
	J[NONE]=I[NONE];
	J[b]=I[b]+MID; 
    J[a]=I[a]-MID;
    J[3]=I[3]+1;
	return 1;
}



void move(int now)
{
	int J[4];int i,j;
	if(flag==0)return ;
	
	for(i=0;i<3;i++)
	   for(j=0;j<3;j++)
	{
	if(dao_a2b(J,i,j,N[now])){
	if(judge(J)){   
	N[n][0]=J[0]; N[n][1]=J[1]; N[n][2]=J[2]; N[n][3]=J[3]; n++;
	}}
	
   }


}

int bfs(){
	int i,j;
	
	scanf("%d%d%d",&S,&A,&B);
	if(S==0&&A==0&&B==0)return 0;
	if(S==0){printf("0\n");return 1;}
    if(S%2==1){printf("NO\n");return 1;}
    if(A< S/2&&B <S/2){printf("NO\n");return 1;}
    	
	 n=1;flag=1;
	 N[0][0]=S;
	 N[0][1]=0;
	 N[0][2]=0;
	 
	 N[0][3]=0;
    for(i=0;i<n;i++)
	{
		move(i);
    }	
    if(flag==1)printf("NO\n");
    	
	return 1;
}

int main()
{
 while(1){
	if(bfs()==0)break;
}	
	
return 0;	
}
/**************************************************************
	Problem: 2227
	User: admin
	Language: C
	Result: Accepted
	Time:9 ms
	Memory:1152 kb
****************************************************************/