...comenzar...de las

#include <bits/stdc++.h>
using namespace std;
char m[1100], k[110], ans[1100];
int lenm, lenk, j;
bool judge(char s){
    if(s >= 'a' and s <= 'z'){
        return true;
    }else{
        return false;
    }
}
int main(){
    gets(k);
    gets(m);
    lenm = strlen(m);
    lenk = strlen(k);
    for(int i = 0, j = 0; i < lenm; i++, j++){
        if(j >= lenk){
            j = 0;
        }
        if(judge(m[i])){
            if(!judge(k[j])){
                k[j] += 'a' - 'A';
            }
            ans[i] = m[i] - (k[j] - 'a');
            if(ans[i] < 'a'){
                ans[i] += 26;
            }
        }else{
            if(judge(k[j])){
                k[j] -= 'a' - 'A';
            }
            ans[i] = m[i] - (k[j] - 'A');
            if(ans[i] < 'A'){
                ans[i] += 26;
            }
        }
    }
    cout << ans;
    return 0;
}