快速读入

提高读入数据的效率，返回值为第一个读入的整数。

inline int read()
{
	int x = 0, f = 1; char ch = getchar();
	while (ch < '0' || ch>'9'){if (ch == '-') f = -1; ch = getchar();}
	while (ch >= '0' && ch <= '9') {x = x * 10 + ch - 48; ch = getchar();}
	return x * f;
}