为何RE+MLE（爆栈）了?铅条

#include <bits/stdc++.h>
using namespace std;
long long n,a,b,x,y,jl,k,la,lb,d,p1,p2,gcdd,i;
bool pd;
long long gcd1(long long k1,long long k2){
	if(k2==0) return k1;
	return gcd1(k2,k1%k2);
}
long long exgcd(long long s1,long long s2,long long &gcdd,long long &x,long long &y){
	if(s2==0) gcdd=s1,x=1/s1,y=0;
	else{
		long long x1,y1;
		exgcd(s2,s1%s2,gcdd,x1,y1);
		x=y1;
		y=x1-s1/s2*y1;
	}
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin>>n;
    pd=1;
    for(i=1;i<=n;i++){
    	cin>>a>>b;
    	if(i==1){
    		la=a,lb=b;
    		continue;
		}
    	jl=gcd1(la,a);
		p1=la/jl,p2=a/jl;
		exgcd(p1,p2,gcdd,x,y);
		lb=(lb+(b-lb)*x*la);
		la=a/gcd1(la,a)*la;
		lb=lb%la;
	} 
	while(lb<0) lb+=la;
	lb=lb%la;
	cout<<lb;
    return 0;
}