Kick Start 2022 Round A 2022 Speed Typing

#include <bits/stdc++.h>
using namespace std;
string solve(string& origin, string& problem) {
    if(problem.length() < origin.length()) return "IMPOSSIBLE";
    int i = 0, j = 0;
    while(i < origin.length() and j < problem.length()) {
        if(origin[i] == problem[j]) {
            i++;j++;
        } else {
            j++;
        }
    }
    if(i == origin.length()) {
        return to_string(problem.length() - origin.length());
    }
    return "IMPOSSIBLE";
}
int main() {
    int t;
    cin>>t;
    for(int i = 1; i <= t; i++) {
        string o, p;
        cin>>o>>p;
        cout<<"Case #"<<i<<": "<< solve(o,p)<<endl;
    }
    return 0;
}