Submission #3388134

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Source Code Expand

#include <bits/stdc++.h>

#define For(i, j, k) for (int i = j; i <= k; ++ i)
#define Forr(i, j, k) for (int i = j; i >= k; -- i)

typedef long long ll;

using namespace std;

inline void File() {
	freopen("D.in", "r", stdin);
	freopen("D.out", "w", stdout);
}

ll n, s;

inline ll calc(ll x, ll b) {
	ll res = 0; while (x) res += x % b, x /= b; return res;
}

int main() {

	cin >> n >> s;
	int lim = sqrt(n + 1);		

	For(i, 2, lim) if (calc(n, i) == s) return printf("%d\n", i), 0;

	Forr(x1, lim - 1, 1) { 
		if ((n - s) % x1 > 0) continue;
		ll b = (n - s) / x1 + 1;
		if (b > lim && x1 <= s && s - x1 < b) {
			return printf("%lld\n", b), 0;
		}
	}

	if (n == s) return printf("%lld", n + 1), 0;
	puts("-1");

	return 0;
}

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