呵呵，代码超时

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<cstdlib>
#include<algorithm>
#include<bits/stdc++.h>

using namespace std;
long long a,b,c;
long long ans;
long long lcm(long long b,long long c){
	int r;
	while(c>0){
		r=a%b;
		a=b;
		b=r;
	}
	return 0;
}
int main(){
	cin>>a>>b>>c;
	long long len=lcm(b,c); 
	for(long long i=1;i<=a;i+=len){
		ans+=i;
	}
	cout<<ans;
	return 0;
}