25. Sum of Numbers in String C++

#include <iostream>
#include <string>
#include <cctype>

int SumNumbers(const std::string&);

int main()
{
    std::string s;
    std::cin >> s;

    std::cout << SumNumbers(s) << std::endl;

    return 0;
}

int SumNumbers(const std::string& s)
{
    int sum = 0;
    for (char ch : s)
        if (std::isdigit(ch))
            sum += ch - '0';

    return sum;
}