function Main(input) {
    var S = input.trim();
    var count = 0;
    for(var i = 0; i < S.length; i++){
        if(S.charAt(i) == 'x'){
            count++;
        }
    }
    var output;
    if(count > 7){
        output = "NO";
    }
    else{
        output = "YES";
    }
    console.log(output);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));