int read() 
{
    char ch=getchar(); 
	int x=0,f=1; 
    while(ch<'0'||ch >'9')
	{
        if(ch=='-') 
		{
			f=-1;
        }
        ch=getchar();
    } 
	while('0'<=ch&&ch<='9')
	{
        x=x*10+ch-'0';
        ch=getchar();
    } 
	return x*f;
}