Revise paste Untitled

#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    
    int A = n % 10;
    int B = (n / 10) % 10;
    int C = n / 100;
    int brojac = 0;
    for(int i = 100; i <= 999; i += 1) {
        int a = A;
        int b = B;
        int c = C;
        int last_digit = i % 10;
        
        if(last_digit == a) {
            a = -1;
        }
        else if(last_digit == b) {
            b = -1;
        }
        else if(last_digit == c) {
            c = -1;
        }
        int middle_digit = (i / 10) % 10;
        if(middle_digit == a) {
            a = -1;
        }
        else if(middle_digit == b) {
            b = -1;
        }
        else if(middle_digit == c) {
            c = -1;
        }
        int first_digit = i / 100;
        if(first_digit == a) {
            a = -1;
        }
        else if(first_digit == b) {
            b = -1;
        }
        else if(first_digit == c) {
            c = -1;
        }
        if(a == -1 and b == -1 and c == -1) {
            brojac += 1;
        }
        
    }
    cout << brojac << endl;
    return 0;
}