一、题目:
洛谷模板
二、代码:
#include<iostream>
#include<cstdio>
#include<cstring>
#define LL long long
#define mem(s,v) memset(s,v,sizeof(s))
#define FILE(s) freopen(s".in","r",stdin);freopen(s".out","w",stdout)
using namespace std;
template<class Type>
inline Type read(Type num){
Type x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return f*x;
}
const int maxn=100005;
int n;
LL ai[maxn],bi[maxn];
inline LL mult(LL a,LL b,LL p){
LL ret=0;
for(;b;b>>=1){
if(b&1)ret=(ret+a)%p;
a=(a+a)%p;
}
return ret;
}
inline LL exgcd(LL a,LL b,LL &x,LL &y){
if(b==0){x=1;y=0;return a;}
LL d=exgcd(b,a%b,x,y);
LL z=x;x=y;y=z-a/b*y;
return d;
}
inline LL excrt(void){
LL x,y;
LL M=bi[1],ans=ai[1];
for(register int i=2;i<=n;++i){
LL a=M,b=bi[i],c=(ai[i]-ans%b+b)%b;
LL gcd=exgcd(a,b,x,y),bg=b/gcd;
if(c%gcd!=0)return -1;
x=mult(x,c/gcd,bg);
ans+=x*M;
M*=bg;
ans=(ans%M+M)%M;
}
return (ans%M+M)%M;
}
int main(){
n=read(n);
for(register int i=1;i<=n;++i){
bi[i]=read(bi[i]);
ai[i]=read(ai[i]);
}
printf("%lld\n",excrt());
return 0;
}