需要10^30才可以存，我们可以用__int128来算

#include<bits/stdc++.h>

using namespace std;

bool is_sqr(__int128 x) {
  __int128 l = -1, r = 1e16;
  while (r - l > 1) {
    __int128 m = (l + r) / 2;
    __int128 m2 = m * m;
    if (m2 <= x) {
      l = m;
    } else {
      r = m;
    }
  }
  if (l * l == x) {
    return true;
  } else {
    return false;
  }
}

long long cnt(__int128 x) { // >=x
  __int128 l = -1, r = 1e16;
  while (r - l > 1) {
    __int128 m = (l + r) / 2;
    __int128 m2 = m * m;
    if (m2 >= x) {
      r = m;
    } else {
      l = m;
    }
  }
  return r;
}

long long range(__int128 l, __int128 r) {
  return cnt(r + 1) - cnt(l);
}

int main() {
  int n;
  cin >> n;
  string L, R;
  cin >> L >> R;

  int m = n / 2;

  __int128 L1 = 0, R1 = 0;
  for (int i = 0; i < m; i++) {
    L1 = L1 * 10 + (L[i] - '0');
    R1 = R1 * 10 + (R[i] - '0');
  }
  __int128 L2 = 0, R2 = 0;
  for (int i = m; i < n; i++) {
    L2 = L2 * 10 + (L[i] - '0');
    R2 = R2 * 10 + (R[i] - '0');
  }
  if (L1 == R1) {
    if (!is_sqr(L1)) {
      cout << 0 << "\n";
      return 0;
    } else {
      cout << range(L2, R2) << "\n";
      return 0;
    }
  }

  __int128 base = 1;
  for (int i = 0; i < m; i++) {
    base = base * 10;
  }

  __int128 ans = 0;
  if (is_sqr(L1)) {
    ans += range(L2, base - 1);
  }

  ans += (__int128)range(L1 + 1, R1 - 1) * range(0, base - 1);

  if (is_sqr(R1)) {
    ans += range(0, R2);
  }


  static int st[35];
  int c = 0;
  do {
    st[++c] = ans % 10;
    ans /= 10;
  } while (ans);

  while (c) {
    cout << st[c];
    c--;
  }
}