快读，快输 比scanf和printf快

int read() {
int res = 0;
char c = getchar();
while (!isdigit(c)) c = getchar();
while (isdigit(c)) res = (res << 1) + (res << 3) + c - 48, c = getchar();
return res;
}
void printi(int x) {
if (x / 10) printi(x / 10);
putchar(x % 10 + '0');
}