Read a sequence of words from cin and store the values a
vector. After you’ve read all the words, process the vector and change
each word to uppercase. Print the transformed elements, eight words to a
line.

Ho scritto il codice e funziona tutto tranne la parte del testo dell'esercizio in grassetto.

codice:
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main()
{

vector<string> s;
cout<<"Scrivi delle parole"<<endl;
string z;
while(cin>>z)
    s.push_back(z);

for(auto &c:s){
for(char &x:c)
x=toupper(x);}

int i=0;

for(auto &c:s)
{
    ++i;
    if(i<=8){
        cout<<c<<" ";
    }
    else{
        cout<<'\n'<<c;
        i=0;
    }


}

}