Revise paste Untitled

#include <iostream>
#include <vector>

void write_numbers(std::string &s, std::vector<int> &numbers) {
    for(int i = 0; i < (int) s.size(); i++) {
        int j = i, cnt = 0;
        while(j < (int) s.size() and s[i] == s[j]) {
            ++cnt;
            ++j;
        }
        i = j - 1;
        numbers.push_back(cnt);
    }
}
void write_characters(std::string &s, std::vector<char> &characters) {
    for(int i = 0; i < (int) s.size(); i++) {
        int j = i;
        char c = s[i];
        while(j < (int) s.size() and s[i] == s[j]) {
            ++j;
        }
        i = j - 1;
        characters.push_back(c);
    }
}

void solve() {
    std::string s;
    std::cin >> s;
    
    try{
        for(int i = 0; i < (int) s.size(); i++) {
            if(s[i] >= 'A' and s[i] <= 'Z') {
                throw "Invalid input!";
            }
            if(s[i] >= '0' and s[i] <= '9') {
                throw "Invalid input!";
            }
            
        }
    }
    catch(const char *c) {
        std::cout << c << std::endl;
        return;
    }

std::vector<int> numbers;
    std::vector<char> characters;
    
    write_numbers(s, numbers);
    write_characters(s, characters);
    
    for(int i = 0; i < (int) numbers.size(); i++) {
        std::cout << numbers[i] << characters[i];
    }
    std::cout << std::endl;
}
int main() {
    solve();
    return 0;
}