task60.vala

string task(string str){
    var result = "";
    unichar c;
    for (int i = 0; str.get_next_char (ref i, out c);) {
        if (c ==' ')result+="%20";
        else result+=c.to_string();
    }
    return result;
}

void main(){
   print(@" $(task("rar ror rer"))");
}