#include <bits/stdc++.h> inline int read() { int res = 0, tag = 1; char c = getchar(); while (c < 48 || c > 57) { if (c == '-') tag = -1; c = getchar(); } while (c >= 48 && c <= 57) { res = (res << 3) + (res << 1) + (c ^ 48); c = getchar(); } return res * tag; } inline void write(int x) { if (x < 0) { putchar('-'); x = -x; } if (x > 9) write(x / 10); putchar(x % 10 + '0'); } const int MX = 1e6; struct node { int val, l, r; }; int tot; struct node a[MX]; int build(std::string s) { std::vector<int> stk(s.size()); int k = 0, f = 0, t = 0; for (int i = 0; i < s.size(); ++i) { if (isdigit(s[i])) k = (k << 1) + (k << 3) + (s[i] ^ 48); else { if (k) { a[++tot] = {k, -1, -1}; if (f == 1) a[stk[t]].l = tot; if (f == 2) a[stk[t]].r = tot; k = 0; } if (s[i] == '(') { stk[++t] = tot; f = 1; } else if (s[i] == ',') { f = 2; } else if (s[i] == ')') { --t; } } } return stk[1]; } int find(int rot, int x){ if (rot == -1) return 0; else if (a[rot].val > x) return find(a[rot].l, x); else if (a[rot].val < x) return find(a[rot].r, x); return rot; } void insert(int &rot, int x) { if (rot == -1) { a[++tot] = {x, -1, -1}; rot = tot; } else if (a[rot].val > x) { insert(a[rot].l, x); } else if (a[rot].val < x) { insert(a[rot].r, x); } } void print(int rot) { if (rot == -1) return; write(a[rot].val); if (a[rot].l == -1 && a[rot].r == -1) return; putchar('('); print(a[rot].l); putchar(','); print(a[rot].r); putchar(')'); } std::vector<int> ans; void inorder(int rot) { if (rot == -1) return; inorder(a[rot].l); ans.push_back(a[rot].val); inorder(a[rot].r); } bool judge() { inorder(1); for (int i = 1; i < ans.size(); ++i) if (ans[i] <= ans [i - 1]) return false; return true; } signed main() { std::string s; std::cin >> s; int rot = build(s); puts(judge() ? "yes" : "no"); return 0; }