read 函数
inline int read() { int x=0,f=1; char c=getchar(); while(c<'0'||c>'9') {if(c=='-') f=-1; c=getchar();} while(c>='0'&&c<='9') {x=x*10+c-'0'; c=getchar();} return f*x; }
write 函数
inline void write(int x) { if(x<0) {putchar('-'); x=-x;} if(x>9) write(x/10); putchar(x%10+'0'); }