int a[NN],b[NN],n;
	//ax=b(mod c)
	int solve()
	{
		int i,k,d,tmp,tmp2;
		for(i=2;i<=n;i++)
		{
			tmp=a[i-1]-a[i];
			if(tmp<0)tmp=b[i-1]-(-tmp)%b[i-1];
			d=gcd(b[i],b[i-1]);
			if(tmp%d>0)return -1;
			exgcd(b[i]/d,b[i-1]/d,k,tmp2);
			k*=tmp/d;
			if(k<0)k=b[i-1]-(-k)%b[i-1];
			else k%=b[i-1];
			//printf("%d * %d = %d mod %d\n",b[i],k,tmp,b[i-1]);
			//printf("x= %d * %d + %d\n",k,b[i],a[i]);
			a[i]=k*b[i]+a[i];
			b[i]=lcm(b[i],b[i-1]);
			a[i]%=b[i];
			//printf("x mod %d = %d\n",b[i],a[i]);
		}
		return a[n];
	}