一、题目：

二、代码：

#include
    
     #include
     
      #include
      
       #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
       
        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;}