813B-TheGoldenAge.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <climits>

int main(){

    const int N = 60; //binary log 10^18
    int64_t x, y, l, r; std::cin >> x >> y >> l >> r;
    std::vector<int64_t> v; v.push_back(l - 1); v.push_back(r + 1);
    int64_t powx = 1;
    for(int a = 0; a < N; a++){
        int64_t powy = 1;
        for(int b = 0; b < N; b++){
            int64_t cand = powx + powy;
            if(l <= cand && cand <= r){int64_t z = cand; v.push_back(z);}
            if(powy > LLONG_MAX / y){break;}
            powy *= y;
        }

        if(powx > LLONG_MAX / x){break;}
        powx *= x;
    }


    sort(v.begin(), v.end());
    int64_t golden(0);
    for(long p = 1; p < v.size(); p++){
        int64_t diff = v[p] - v[p - 1] - 1;
        golden = (golden > diff) ? golden : diff;
    }

    std::cout << golden << std::endl;

    return 0;
}