Decoding the message

#include<bits/stdc++.h>

using namespace std;

char str[1003];

int main()
{
    int test,i,j,k,len,x;

    string s;

    scanf("%d",&test);

    getchar();

    getchar();

    for(x=1; x<=test; x++)
    {
        i = 0;

        int cnt = 1,take = 1;

        bool found = true;

        printf("Case #%d:\n",x);

        while(gets(str) && str[0])
        {
            len = strlen(str);

            s="";

            for(k=0; k<len; k++)
            {
                if((str[k]>='a' && str[k]<='z')||(str[k]>='A' && str[k]<='Z'))
                {
                    while(str[k]!=' ' && str[k]!='\0')
                    {
                        if(cnt==take && found)
                        {
                            s+=str[k];

                            take++;

                            cnt = 1;

                            found = false;
                        }

                        cnt++;

                        k++;
                    }

                    if(str[k]==' ')
                    {
                        cnt = 1;
                    }
                }

                found = true;
            }

            printf("%s\n",s.c_str());

            cnt = 1;

            take = 1;
        }

        if(x<test)
            puts("");
    }

    return 0;
}