90分TLE求助

#include <bits/stdc++.h>
#define int long long
using namespace std;
int a,b;
int l=-2e9+1,r=2e9+1;
signed main(){
	srand(time(0));
	cin>>a>>b;
	while(1){
		int x=rand()%(r-l+1);
		int m=(l+x);
		if(m>r) continue;
		if(m-a==b){
			cout<<m<<"\n";
			return 0; 
		}
		if(m-a>b){
			r=m;
		}else{
			l=m;
		}
	}
	return 0;
}