Problem p03200 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cmath>
#include <iostream>
#include <map>
#include <stdio.h>
#include <vector>
using namespace std;
#define int long long
#define rep(s, i, n) for (int i = s; i < n; i++)
#define c(n) cout << n << endl;
#define ic(n)                                                                  \
  int n;                                                                       \
  cin >> n;
#define sc(s)                                                                  \
  string s;                                                                    \
  cin >> s;
#define mod 1000000007
#define inf 1000000000000000007
#define f first
#define s second
#define mini(c, a, b) *min_element(c + a, c + b)
#define maxi(c, a, b) *max_element(c + a, c + b)
// printf("%.12Lf\n",);
int keta(int x) {
  rep(0, i, 30) {
    if (x < 10) {
      return i + 1;
    }
    x = x / 10;
  }
}
int gcd(int x, int y) {
  int aa = x, bb = y;
  rep(0, i, 1000) {
    aa = aa % bb;
    if (aa == 0) {
      return bb;
    }
    bb = bb % aa;
    if (bb == 0) {
      return aa;
    }
  }
}
int lcm(int x, int y) {
  int aa = x, bb = y;
  rep(0, i, 1000) {
    aa = aa % bb;
    if (aa == 0) {
      return x / bb * y;
    }
    bb = bb % aa;
    if (bb == 0) {
      return x / aa * y;
    }
  }
}
bool p(int x) {
  if (x == 1)
    return false;
  rep(2, i, sqrt(x) + 1) {
    if (x % i == 0 && x != i) {
      return false;
    }
  }
  return true;
}
int max(int a, int b) {
  if (a >= b)
    return a;
  else
    return b;
}
int min(int a, int b) {
  if (a >= b)
    return b;
  else
    return a;
}
int n2[41];
int nis[41];
int nia[41];
int mody[41];
int nn;
int com(int n, int y) {
  int ni = 1;
  for (int i = 0; i < 41; i++) {
    n2[i] = ni;
    ni *= 2;
  }
  int bunsi = 1, bunbo = 1;
  rep(0, i, y) bunsi = (bunsi * (n - i)) % mod;
  rep(0, i, y) bunbo = (bunbo * (i + 1)) % mod;
  mody[0] = bunbo;
  rep(1, i, 41) {
    bunbo = (bunbo * bunbo) % mod;
    mody[i] = bunbo;
  }
  rep(0, i, 41) nis[i] = 0;
  nn = mod - 2;
  for (int i = 40; i >= 0; i -= 1) {
    if (nn > n2[i]) {
      nis[i]++;
      nn -= n2[i];
    }
  }
  nis[0]++;
  rep(0, i, 41) {
    if (nis[i] == 1) {
      bunsi = (bunsi * mody[i]) % mod;
    }
  }
  return bunsi;
}
int yakuwa(int n) {
  int sum = 0;
  rep(1, i, sqrt(n + 1)) {
    if (n % i == 0)
      sum += i + n / i;
    if (i * i == n)
      sum -= i;
  }
  return sum;
}
bool hei(int n) {
  rep(0, i, 100) {
    if (i * i == n) {
      return true;
    }
  }
  return false;
}
int pow(int b, int a) {
  int aa = 1;
  rep(0, i, a) aa *= b;
  return aa;
}
int sum[114514];
signed main() {
  sc(s) int n = s.size();
  int bcnt = 0;
  int ans = 0;
  rep(0, i, n) {
    if (s[i] == 'B')
      bcnt++;
    else
      sum[i - bcnt] = bcnt;
  }
  rep(0, i, n - bcnt) ans += sum[i];
  c(ans)
}

Fixed submission:
#include <algorithm>
#include <cmath>
#include <iostream>
#include <map>
#include <stdio.h>
#include <vector>
using namespace std;
#define int long long
#define rep(s, i, n) for (int i = s; i < n; i++)
#define c(n) cout << n << endl;
#define ic(n)                                                                  \
  int n;                                                                       \
  cin >> n;
#define sc(s)                                                                  \
  string s;                                                                    \
  cin >> s;
#define mod 1000000007
#define inf 1000000000000000007
#define f first
#define s second
#define mini(c, a, b) *min_element(c + a, c + b)
#define maxi(c, a, b) *max_element(c + a, c + b)
// printf("%.12Lf\n",);
int keta(int x) {
  rep(0, i, 30) {
    if (x < 10) {
      return i + 1;
    }
    x = x / 10;
  }
}
int gcd(int x, int y) {
  int aa = x, bb = y;
  rep(0, i, 1000) {
    aa = aa % bb;
    if (aa == 0) {
      return bb;
    }
    bb = bb % aa;
    if (bb == 0) {
      return aa;
    }
  }
}
int lcm(int x, int y) {
  int aa = x, bb = y;
  rep(0, i, 1000) {
    aa = aa % bb;
    if (aa == 0) {
      return x / bb * y;
    }
    bb = bb % aa;
    if (bb == 0) {
      return x / aa * y;
    }
  }
}
bool p(int x) {
  if (x == 1)
    return false;
  rep(2, i, sqrt(x) + 1) {
    if (x % i == 0 && x != i) {
      return false;
    }
  }
  return true;
}
int max(int a, int b) {
  if (a >= b)
    return a;
  else
    return b;
}
int min(int a, int b) {
  if (a >= b)
    return b;
  else
    return a;
}
int n2[41];
int nis[41];
int nia[41];
int mody[41];
int nn;
int com(int n, int y) {
  int ni = 1;
  for (int i = 0; i < 41; i++) {
    n2[i] = ni;
    ni *= 2;
  }
  int bunsi = 1, bunbo = 1;
  rep(0, i, y) bunsi = (bunsi * (n - i)) % mod;
  rep(0, i, y) bunbo = (bunbo * (i + 1)) % mod;
  mody[0] = bunbo;
  rep(1, i, 41) {
    bunbo = (bunbo * bunbo) % mod;
    mody[i] = bunbo;
  }
  rep(0, i, 41) nis[i] = 0;
  nn = mod - 2;
  for (int i = 40; i >= 0; i -= 1) {
    if (nn > n2[i]) {
      nis[i]++;
      nn -= n2[i];
    }
  }
  nis[0]++;
  rep(0, i, 41) {
    if (nis[i] == 1) {
      bunsi = (bunsi * mody[i]) % mod;
    }
  }
  return bunsi;
}
int yakuwa(int n) {
  int sum = 0;
  rep(1, i, sqrt(n + 1)) {
    if (n % i == 0)
      sum += i + n / i;
    if (i * i == n)
      sum -= i;
  }
  return sum;
}
bool hei(int n) {
  rep(0, i, 100) {
    if (i * i == n) {
      return true;
    }
  }
  return false;
}
int pow(int b, int a) {
  int aa = 1;
  rep(0, i, a) aa *= b;
  return aa;
}
int sum[214514];
signed main() {
  sc(s) int n = s.size();
  int bcnt = 0;
  int ans = 0;
  rep(0, i, n) {
    if (s[i] == 'B')
      bcnt++;
    else
      sum[i - bcnt] = bcnt;
  }
  rep(0, i, n - bcnt) ans += sum[i];
  c(ans)
}