A

#include<iostream>
#include<cstring>
#include<algorithm>
#include<string>
using namespace std;
const int N = 1e5 + 10;
int main()
{
    string a;
    getline(cin, a);
    for (int i = 0; i < a.size(); i++)
    {
        if (a[i] >= 'A' && a[i] <= 'Z')
        {
            char op = a[i];
            op -= 5;
            if (op < 'A') op = op - 'A' + 'Z'+1;
            cout << op;
        }
        else cout << a[i];
    }

    return 0;
}

B

#include<iostream>
using namespace std;
int main()
{
    int n,k;
    while(cin>>n>>k)
    {
        int t=1;
        int m=n;
        double h=200;
        while(t<=20)
        {
            if(m>=h)
            {
                cout<<t<<endl;
                break;
            }
            m=m+n;
            h=h*(1+0.01*k);
            t++;
        }
        if(t>20)cout<<"Impossible"<<endl;
    }
    return 0;
}

C

#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n;
    cin >> n;
    int flag = 0;
    int happy = 0;
    for (int i = 1; i <=n; i++) 
    {
        int a, b;
        cin>>a>>b;
        int sum = b / a;
        if (sum > happy) 
        {
            happy = b / a;
            flag = i;
        }
    }
    cout << flag;
    return 0;
}