Submission #36821253

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Source Code Expand

#include<bits/stdc++.h>
#ifdef xay5421
#define D(...) fprintf(stderr,__VA_ARGS__)
#define DD(...) D(#__VA_ARGS__ "="),debug_helper::debug(__VA_ARGS__),D("\n")
#include"/home/xay5421/debug.hpp"
#else
#define D(...) ((void)0)
#define DD(...) ((void)0)
#endif
#define pb push_back
#define eb emplace_back
#define SZ(x) ((int)(x).size())
#define each(x,v) for(auto&x:v)
#define rep(i,a,b) for(int i=(a);i<=(b);++i)
#define per(i,a,b) for(int i=(a);i>=(b);--i)
template<class T>void rd(T&x){int f=0,c;while(!isdigit(c=getchar()))f^=!(c^45);x=(c&15);while(isdigit(c=getchar()))x=x*10+(c&15);if(f)x=-x;}
template<class T>void pt(T x,int c=-1){if(x<0)putchar('-'),x=-x;if(x>9)pt(x/10);putchar(x%10+48);if(c!=-1)putchar(c);}
using namespace std;
using LL=long long;
using ULL=unsigned long long;
const int P=200003;
int ad(int k1,int k2){return k1+k2>=P?k1+k2-P:k1+k2;}
int su(int k1,int k2){return k1-k2<0?k1-k2+P:k1-k2;}
int mu(int k1,int k2){return 1ULL*k1*k2%P;}
void uad(int&k1,int k2){(k1+=k2)>=P&&(k1-=P);}
void usu(int&k1,int k2){(k1-=k2)<0&&(k1+=P);}
template<class... T>int ad(int k1,T... k2){return ad(k1,ad(k2...));}
template<class... T>int su(int k1,T... k2){return su(k1,ad(k2...));}
template<class... T>int mu(int k1,T... k2){return mu(k1,mu(k2...));}
template<class... T>void uad(int&k1,T... k2){return uad(k1,ad(k2...));}
template<class... T>void usu(int&k1,T... k2){return usu(k1,ad(k2...));}
int po(int k1,int k2){
	int k3=1;
	for(;k2;k2>>=1,k1=mu(k1,k1))if(k2&1)k3=mu(k3,k1);
	return k3;
}
LL n,m;
int fac[P],ifac[P];
int C(LL n,LL m){
	if(m<0||n<m)return 0;
	if(n<P&&m<P){
		return mu(fac[n],ifac[m],ifac[n-m]);
	}else{
		return mu(C(n%P,m%P),C(n/P,m/P));
	}
}
int main(){
	fac[0]=1;
	rep(i,1,P-1)fac[i]=mu(fac[i-1],i);
	ifac[P-1]=po(fac[P-1],P-2);
	per(i,P-1,1)ifac[i-1]=mu(ifac[i],i);
	rd(n),rd(m);
	m-=n;
	auto Get=[&](LL k){ // 1/(1-x)^2k
		return C(n*2+k-1,k);
	};
	int ans=0;
	uad(ans,Get(m));
	for(int i=1;;++i){
		LL t=1LL*i*(i*3-1)/2;
		if(t<=m){
			uad(ans,mu(i&1?P-1:1,Get(m-t)));
		}else break;
	}
	for(int i=1;;++i){
		LL t=1LL*i*(i*3+1)/2;
		if(t<=m){
			uad(ans,mu(i&1?P-1:1,Get(m-t)));
		}else break;
	}
	printf("%d\n",ans);
	return 0;
}

Submission Info

Judge Result