1 int read()
 2 {
 3     int ret=0;
 4     char c=getchar();
 5     while (c<‘0‘ || c>‘9‘){
 6         c=getchar();
 7     }        
 8     while (c>=‘0‘&&c<=‘9‘){
 9         ret=(ret<<1)+(ret<<3)+c-‘0‘;
10         c=getchar();
11     }
12     return ret;
13 }