提交时间:2024-11-12 21:20:33
运行 ID: 34721
#include<bits/stdc++.h> using namespace std; #define int long long const int MOD=1e9+7,N=1e5+10; int l,r; int pre[N]; int ind1,ind2,ans1,ans2,ans; void init(){ for(int i=0;i<N;i++) pre[i]=i*i; ans1=ans2=0; } int add(int x,int y){ return (x+y)*(y-x+1)/2; } signed main(){ //freopen("alice.in","r",stdin); //freopen("alice.out","w",stdout); init(); scanf("%lld%lld",&l,&r); ind1=lower_bound(pre,pre+N,l)-pre; ind2=lower_bound(pre,pre+N,r)-pre; if(pre[ind1]!=l){ ind1--; for(int i=pre[ind1];i<=l-1;i++){ if(pre[ind1+(i-pre[ind1]>pre[ind1+1]-i)]%2) ans1+=i; else ans1-=i; ans1%=MOD; } } //cout<<ans1<<' '; if(pre[ind2]!=r){ ind2--; for(int i=pre[ind2];i<=r;i++){ if(pre[ind2+(i-pre[ind2]>pre[ind2+1]-i)]%2) ans2+=i; else ans2-=i; ans2%=MOD; } } //cout<<ans2<<' '; ans=ans2-ans1; ans%=MOD; //cout<<ans<<endl; if(ans<0){ ans=MOD+ans; } printf("%lld",ans); return 0; }