#include <iostream>
using namespace std;

int* fillRing(int n) {
    int* ring = new int[n];
    for(int i = 0; i < n; i++) {
        ring[i] = i;
    }

    return ring;
}

int add(int left, int right, int n) {
    if(left > n || right > n) {
        return -1;
    }
    return (left + right) % n;
}

int subract(int left, int right, int n) {
    if(left > n || right > n) {
        return -1;
    }

    int res = left - right;
    if(res < 0) {
        res = n + res;
    }

    return res;
}

int multiply(int left, int right, int n) {
    if(left > n || right > n) {
        return -1;
    }

    return (left * right) % n;
}

int** fillPairs(int n) {
    int** result = new int*[2];
    result[0] = new int[n];
    result[1] = new int[n];
    int c = 0;

    for(int i = 1; i < n; i++) {
        for(int j = 1; j < n; j++) {
            unsigned int mult = j*i;
            if((mult % n) == 1) {
                result[0][c] = i;
                result[1][c] = j;
                c++;
            }
        }
    }

    result[0][c] = -1; // Last element;
    result[1][c] = -1; // Last element;

    return result;
}
int main() {
    int n = 7;
    int* ring = fillRing(n);
    cout << add(0, 4, n) << endl;
    cout << add(3, 4, n) << endl;
    cout << add(2, 6, n) << endl;
    cout << add(4, 5, n) << endl;
    cout << subract(2, 5, n) << endl;
    cout << subract(1, 3, n) << endl;
    cout << subract(4, 5, n) << endl;
    cout << multiply(2, 6, n) << endl;
    cout << multiply(4, 4, n) << endl;
    cout << multiply(5, 5, n) << endl;

    int **pairs = fillPairs(n);

    int i = 0;
    while(pairs[0][i] != -1) {
        cout << pairs[0][i] << " * " << pairs[1][i] << " % " << n << " = 1" << endl;
        i++;
    }


    return 0;
}