zoj 1879 Jolly Jumpers

#include<stdio.h>#include<string.h>#include<math.h>#include<stdlib.h>int N;int main(){  int dif[3001];  int a,b,i;  int flag;  while(scanf("%d",&N)==1)  {    for(i=0;i<3000;i++)    {      dif[i]=0;    }    flag=1;    scanf("%d",&a);    if(N==1)    {      printf("Jollyn");      continue;    }    for(i=2;i<=N;i++)    {      scanf("%d",&b);      dif[abs(a-b)]=1;      a=b;    }    for(i=1;i<=N-1;i++)    {      if(dif[i]!=1)      {        flag=0;      }    }    if(flag)    {      printf("Jollyn");    }    else     {      printf("Not jollyn");    }  }  return 0;}