Problem p02873 (C++)

Buggy submission (status: Runtime Error):
/*input
<>>><<><<<<<>>><
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag,
             tree_order_statistics_node_update>
    indexed_set;
#pragma GCC optimize("unroll-loops,no-stack-protector")
// order_of_key #of elements less than x
//  find_by_order kth element
typedef long long int ll;
#define ld long double
#define pii pair<ll, ll>
#define f first
#define s second
#define pb push_back
#define REP(i, n) for (int i = 0; i < n; i++)
#define REP1(i, n) for (int i = 1; i <= n; i++)
#define FILL(n, x) memset(n, x, sizeof(n))
#define ALL(_a) _a.begin(), _a.end()
#define sz(x) (int)x.size()
const ll maxn = 200005;
const ll maxlg = __lg(maxn) + 2;
const ll INF64 = 4000000000000000LL;
const int INF = 0x3f3f3f3f;
const ll MOD = ll(1e9 + 7);
const ld PI = acos(-1);
const ld eps = 1e-9;
#define lowb(x) x & (-x)
#define MNTO(x, y) x = min(x, (__typeof__(x))y)
#define MXTO(x, y) x = max(x, (__typeof__(x))y)
ll mult(ll a, ll b) { return ((a % MOD) * (b % MOD)) % MOD; }
ll mypow(ll a, ll b) {
  if (b <= 0)
    return 1;
  ll res = 1LL;
  while (b) {
    if (b & 1)
      res = mult(res, a);
    a = mult(a, a);
    b >>= 1;
  }
  return res;
}
int arr[maxn];
int main() {
  string s;
  cin >> s;
  arr[0] = 0;
  REP1(i, s.length()) {
    if (s[i - 1] == '<')
      MXTO(arr[i], arr[i - 1] + 1);
  }
  ll ans = arr[s.length()];
  for (int i = s.length() - 1; i >= 0; i--) {
    if (s[i] == '>')
      MXTO(arr[i], arr[i + 1] + 1);
    ans += arr[i];
  }
  cout << ans;
}

Fixed submission:
/*input
<>>><<><<<<<>>><
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag,
             tree_order_statistics_node_update>
    indexed_set;
#pragma GCC optimize("unroll-loops,no-stack-protector")
// order_of_key #of elements less than x
//  find_by_order kth element
typedef long long int ll;
#define ld long double
#define pii pair<ll, ll>
#define f first
#define s second
#define pb push_back
#define REP(i, n) for (int i = 0; i < n; i++)
#define REP1(i, n) for (int i = 1; i <= n; i++)
#define FILL(n, x) memset(n, x, sizeof(n))
#define ALL(_a) _a.begin(), _a.end()
#define sz(x) (int)x.size()
const ll maxn = 500005;
const ll maxlg = __lg(maxn) + 2;
const ll INF64 = 4000000000000000LL;
const int INF = 0x3f3f3f3f;
const ll MOD = ll(1e9 + 7);
const ld PI = acos(-1);
const ld eps = 1e-9;
#define lowb(x) x & (-x)
#define MNTO(x, y) x = min(x, (__typeof__(x))y)
#define MXTO(x, y) x = max(x, (__typeof__(x))y)
ll mult(ll a, ll b) { return ((a % MOD) * (b % MOD)) % MOD; }
ll mypow(ll a, ll b) {
  if (b <= 0)
    return 1;
  ll res = 1LL;
  while (b) {
    if (b & 1)
      res = mult(res, a);
    a = mult(a, a);
    b >>= 1;
  }
  return res;
}
int arr[maxn];
int main() {
  string s;
  cin >> s;
  arr[0] = 0;
  REP1(i, s.length()) {
    if (s[i - 1] == '<')
      MXTO(arr[i], arr[i - 1] + 1);
  }
  ll ans = arr[s.length()];
  for (int i = s.length() - 1; i >= 0; i--) {
    if (s[i] == '>')
      MXTO(arr[i], arr[i + 1] + 1);
    ans += arr[i];
  }
  cout << ans;
}