好多种版本，今天给出其中之一，也是比较快的一种。 

int read() {char ch = getchar();int num = 0;bool fl = 0;for(; !isdigit(ch); ch = getchar())if (ch=='-') fl = 1;for(; isdigit(ch); ch = getchar())num = (num<<1)+(num<<3)+ch-48;if(fl) num = -num;return num;
}

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

__int128相关知识点

 

再来个超快版本：（真の超快，用这个板子在vj上刷到了好多榜一）

inline char nc() {static char buf [100000],*p1=buf,*p2=buf;return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;
}
inline int read() {static char c=nc(); int x=0,f=1;for(;c>'9'||c<'0';c=nc()) if(c=='-') f=-1;for(;c<='9'&&c>='0';c=nc()) x=(x<<3)+(x<<1)+c-48;return x*f;
}