#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <typename T>
using PQ = priority_queue<T>;
template <typename T>
using GPQ = priority_queue<T, vector<T>, greater<T>>;
template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> p);
template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
  os << "[";
  for (auto vv : v) os << vv << ",";
  return os << "]";
}
template <class T>
ostream& operator<<(ostream& os, set<T> v) {
  os << "[";
  for (auto vv : v) os << vv << ",";
  return os << "]";
}
template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> p) {
  return os << "(" << p.first << "," << p.second << ")";
}
template <typename T>
inline T sq(T a) {
  return a * a;
}
template <typename T>
T gcd(T a, T b) {
  if (a > b) return gcd(b, a);
  return a == 0 ? b : gcd(b % a, a);
}
template <typename T, typename U>
T mypow(T b, U n) {
  if (n == 0) return 1;
  if (n == 1) return b;
  if (n % 2 == 0) {
    return mypow(b * b, n / 2);
  } else {
    return mypow(b, n - 1) * b;
  }
}
ll pcnt(ll b) { return __builtin_popcountll(b); }
template <typename T>
T iceil(T n, T d) {
  return (n + d - 1) / d;
}
map<char, int> hand = {{'R', 0}, {'S', 1}, {'P', 2}};
class BIT {
 public:
  explicit BIT(int N, int v) : V_NUM(N) {
    data.resize(N);
    fill(data.begin(), data.end(), v);
  }
  ll query(int i) {
    ll ret = 0;
    while (i > 0) {
      ret += data[i];
      i -= (i & -i);
    }
    return ret;
  }
  void update(int i, int v) {
    while (i < V_NUM) {
      data[i] += v;
      i += (i & -i);
    }
  }
  int_fast32_t V_NUM;
  vector<int> data;
};
int main() {
  int N, Q;
  string S;
  cin >> N >> Q >> S;
  S = "$" + S;
  vector<BIT> bit(3, BIT(N + 1, 0));
  vector<set<int>> pos(3);
  for (int i = 1; i <= N; ++i) {
    bit[hand[S[i]]].update(i, 1);
    pos[hand[S[i]]].insert(i);
  }
  for (int q = 0; q <= Q; ++q) {
    int lose = 0;
    int emp = 0;
    for (int h = 0; h < 3; ++h) {
      if (pos[h].empty()) ++emp;
    }
    if (emp == 1) {
      for (int h = 0; h < 3; ++h) {
        if (pos[h].empty() || pos[(h + 1) % 3].empty()) continue;
        lose = pos[(h + 1) % 3].size();
      }
    } else if (emp == 0) {
      for (int h = 0; h < 3; ++h) {
        int w = (h + 1) % 3, l = (h + 2) % 3;
        int wpos = *(pos[w].begin()), lpos = *(pos[l].begin());
        lose += max(0LL, bit[h].query(wpos) - bit[h].query(lpos));
        wpos = *(--pos[w].end()), lpos = *(--pos[l].end());
        lose += max(0LL, bit[h].query(lpos) - bit[h].query(wpos));
      }
    }
    cout << N - lose << "\n";
    if (q == Q) break;
    int p;
    char c;
    cin >> p >> c;
    bit[hand[S[p]]].update(p, -1);
    pos[hand[S[p]]].erase(p);
    bit[hand[c]].update(p, 1);
    pos[hand[c]].insert(p);
    S[p] = c;
  }
  return 0;
}
