[백준 2745] 진법 변환 (Math) (C/C++)

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <math.h>
using namespace std;
 
int N;
string NUM;
long long ans;
 
void change(string num)
{
    for(int i = num.size()-1; i >= 0; i--)
    {
        int value;
        
        if('A' <= num[i] && num[i] <= 'Z')
        {
            value = num[i]-'A'+ 10;
        }
        else
        {
            value = num[i]-'0';
        }
        
        ans += (value * pow(N, num.size()-1-i));
    }
}
 
int main(void)
{
//    freopen("B2745_input.txt", "r", stdin);
    
    cin >> NUM >> N;
    
    change(NUM);
    
    cout << ans;
    
    return 0;
}