巴蜀1738 曹冲养猪

 1 /*by SilverN*/
 2 #include<algorithm>
 3 #include<iostream>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<cmath>
 7 #define LL long long
 8 using namespace std;
 9 const int mxn=15;
10 LL a[mxn],b[mxn];
11 int n;
12 LL exgcd(LL a,LL b,LL &x,LL &y){
13     if(!b){
14         x=1;y=0;
15         return a;
16     }
17     LL res=exgcd(b,a%b,x,y);
18     LL t=x;x=y;y=t-a/b*x;
19     return res;
20 }
21 LL clc(){
22     LL M=1;
23     LL res=0;
24     int i,j;LL x,y;
25     for(i=1;i<=n;i++){M*=a[i];}
26     for(i=1;i<=n;i++){
27         LL tmp=M/a[i];
28         exgcd(tmp,a[i],x,y);
29         res=(res+tmp*x*b[i])%M;
30     }
31     res=(res+M)%M;
32     return res;
33 }
34 int main(){
35     scanf("%d",&n);
36     int i,j;
37     for(i=1;i<=n;i++){
38         scanf("%d%d",&a[i],&b[i]);
39     }
40     LL ans=clc();
41     printf("%lld\n",ans);
42     return 0;
43 }