Submission #3195629

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define P pair<ll,ll>
#define FOR(I,A,B) for(ll I = (A); I < (B); ++I)
#define FORR(I,A,B) for(ll I = (B-1); I >= (A); --I)
#define SORT(x) (sort(x.begin(),x.end())) // 0 2 2 3 4 5 8 9
#define REV(x) (reverse(x.begin(),x.end())) //reverse
ll gcd(ll a,ll b){if(a<b)swap(a,b);if(a%b==0)return b;else return gcd(b,a%b);}
ll lcm(ll a,ll b){ll c=gcd(a,b);return ((a/c)*(b/c)*c);}//saisyo kobaisu
#define NEXTP(x) next_permutation(x.begin(),x.end())
const ll INF=1e18+7;
const ll MOD=1e9+7;


int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	ll N,ans=0;
	cin>>N;
	ll ans52[53];
	ans52[0]=0;
	FOR(i,1,53)ans52[i]=2-(i&1);
	FOR(i,1,53)ans52[i]+=ans52[i-1];
	if(N<=52){
		cout << ans52[N] << endl;
	}else{
		ans = ans52[52];
		N -= 52;
		ll x = 25*26;
		ll y = 2;
		N-=x;
		ans += x*y;
		if(N<=0){
			ans -= abs(N)*y;
			cout << ans << endl;
			return 0;
		}




		ll k = 26*26*26;
		ll p = 3;
		while(1){
			N -= k;
			ans += p*k;
			if(N<=0){
				ans -= abs(N)*p;
				break;
			}
			k*=26;
			p++;
		}
		cout << ans << endl;
	}
}

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