How can I add a changing integer variable to string ?

there is something wrong in the if condition but it's the 7th day I have no clue .... it prints the taken integer like this >> mike .. mike1 .. mike12 .. mike123 but actually i need it to be like this >> mike .. mike1 .. mike2 .. mike3 so any help ? this is my code :

#include <bits/stdc++.h>

using namespace std;



string str(int o){
stringstream ss;
ss<<o;
return ss.str();}


int main(){

int n;
cin>>n;
int z[n];
for(int p=0;p<n;p++)
{
    z[p]=-50;
}
string x[n];
int k;
for(int i=0;i<n;i++){
    k=1;
    cin>>x[i];
    **for(int j=0;j<i;j++){
        if(x[j]== x[i]){
            x[i] = x[j] + str(k) ;
            k++;
            z[i]=0;
        }**
    }

}

for(int q=0;q<n;q++){
    if(z[q]==0)
        cout<<x[q]<<endl;
    else
        cout<<"OK"<<endl;
}



return 0;
}