#include <iostream>
using namespace std;
int main() {
    long long i, j, iDel; long long biggestV = 9999999, biggestDel = 9999999;
    cin >> i >> j;
    if (i == 1) {
        cout << 1;
        return 0;
    }
    else if (i == j) {
        cout << i;
        return 0;
    }
    else if (i + 1 == j) {
        cout << (j % 2 != 0 ? j : i);
        return 0;
    }
    for (long long iV = j % 2 != 0 ? j : j-1; iV >= i; iV -= 2) {
        for (iDel = j / 3 + 1; iDel >= 1; iDel--) {
            if (iV%iDel == 0) {
                if (iDel < biggestDel) {
                    biggestDel = iDel;
                    biggestV = iV;
                }
                break;
            }
        }
        if (iDel == 1) {
            cout << iV;
            return 0;
        }
    }
    cout << biggestV;
}

In the main cycle you doesn't compare trivialities, you search the smallest biggest divisor in the weird range instead. Could you please show the mathematical proof of your main cycle?

Edited by author 31.03.2020 14:11

Edited by author 31.03.2020 14:12

Hi.Did you solve this problem?