读入优化

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