int n, t;

first while(cin >> n)

and then if (n == 0)break

cin >> t

vector<long long int>a(t + 1, 0)

....

....

....省

....略

....了

....

....

if (c == -1)

ans = false;

else

a[c] = x;

printf("%s\n", ans ? " YES" : "NO");

that's all i can give you