#include <bits/stdc++.h>
using namespace std;
inline int readChar();
template <class T = int>
inline T readInt();
template <class T>
inline void writeInt(T x, char end = 0);
inline void writeChar(int x);
inline void writeWord(const char *s);
static const int buf_size = 4096;
inline int getChar() {
  static char buf[buf_size];
  static int len = 0, pos = 0;
  if (pos == len) pos = 0, len = fread(buf, 1, buf_size, stdin);
  if (pos == len) return -1;
  return buf[pos++];
}
inline int readChar() {
  int c = getChar();
  while (c <= 32) c = getChar();
  return c;
}
template <class T>
inline T readInt() {
  int s = 1, c = readChar();
  T x = 0;
  if (c == '-') s = -1, c = getChar();
  while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = getChar();
  return s == 1 ? x : -x;
}
static int write_pos = 0;
static char write_buf[buf_size];
inline void writeChar(int x) {
  if (write_pos == buf_size)
    fwrite(write_buf, 1, buf_size, stdout), write_pos = 0;
  write_buf[write_pos++] = x;
}
template <class T>
inline void writeInt(T x, char end) {
  if (x < 0) writeChar('-'), x = -x;
  char s[24];
  int n = 0;
  while (x || !n) s[n++] = '0' + x % 10, x /= 10;
  while (n--) writeChar(s[n]);
  if (end) writeChar(end);
}
inline void writeWord(const char *s) {
  while (*s) writeChar(*s++);
}
struct Flusher {
  ~Flusher() {
    if (write_pos) fwrite(write_buf, 1, write_pos, stdout), write_pos = 0;
  }
} flusher;
inline void readWord(char *s) {
  int c = readChar();
  while (c > 32) *s++ = c, c = getChar();
  *s = 0;
}
inline void writeDouble(double x, int output_len) {
  if (x < 0) writeChar('-'), x = -x;
  int t = (int)x;
  writeInt(t), x -= t;
  writeChar('.');
  for (int i = output_len - 1; i > 0; i--) {
    x *= 10;
    t = min(9, (int)x);
    writeChar('0' + t), x -= t;
  }
  x *= 10;
  t = min(9, (int)(x + 0.5));
  writeChar('0' + t);
}
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vll = vector<ll>;
using ull = unsigned long long;
using pnt = complex<ld>;
istream &operator>>(istream &in, pnt &p) {
  ld a, b;
  in >> a >> b;
  p = {a, b};
  return in;
}
ld crs(pnt a, pnt b) { return a.real() * b.imag() - a.imag() * b.real(); }
ld dot(pnt a, pnt b) { return a.real() * b.real() + a.imag() * b.imag(); }
const int mod = 1e9 + 7;
const int inf = 1e9 + 100;
const ll inf64 = 1e18L;
const ld pi = acos(-1.0L);
const ld eps = 1e-9L;
const int di[] = {0, 1, -1, 0};
const int dj[] = {1, 0, 0, -1};
const int SQ = 1000;
const int LG = 21;
const int nax = 1e6 + 100;
const pii neu = make_pair(inf, -inf);
pii comb(pii a, pii b) {
  return make_pair(min(a.first, b.first), max(a.second, b.second));
}
struct segTree {
  int n;
  vector<pii> t;
  segTree(int n) : n(n), t(2 * n, neu) {}
  void upd(int v, pii x) {
    t[v += n] = x;
    for (v >>= 1; v; v >>= 1) t[v] = comb(t[v * 2], t[v * 2 + 1]);
  }
  pii get(int l, int r) {
    pii ret = neu;
    for (l += n, r += n; l <= r; l = (l + 1) >> 1, r = (r - 1) >> 1) {
      if (l & 1) ret = comb(ret, t[l]);
      if (!(r & 1)) ret = comb(ret, t[r]);
    }
    return ret;
  }
};
struct fenwick {
  int n;
  vi t;
  fenwick(int n) : n(n), t(n, 0) {}
  void upd(int v, int x) {
    for (int i = v; i < n; i |= i + 1) t[i] += x;
  }
  int get(int v) {
    int ret = 0;
    for (int i = v; i >= 0; i = (i & (i + 1)) - 1) ret += t[i];
    return ret;
  }
  int get(int l, int r) {
    if (l > r) return 0;
    return get(r) - get(l - 1);
  }
};
int n, q;
string s;
int a[nax];
map<char, int> re;
int getAns(vector<segTree> &t, vector<fenwick> &f) {
  int ret = 0;
  pii _all = make_pair(-inf, inf);
  for (int i = 0; i < 3; i++) {
    pii g = t[i].get(0, n - 1);
    _all.first = max(_all.first, g.first);
    _all.second = min(_all.second, g.second);
  }
  for (int who = 0; who < 3; who++) {
    pii g = t[(who + 1) % 3].get(0, n - 1);
    if (g.first > g.second)
      ret += f[who].get(0, n - 1);
    else
      ret += f[who].get(
                 0, min(g.first - 1, t[(who + 2) % 3].get(0, n - 1).second)) +
             f[who].get(_all.first, _all.second) +
             f[who].get(max(t[(who + 2) % 3].get(0, n - 1).first, g.second + 1),
                        n - 1);
  }
  return ret;
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cout.precision(12);
  cout << fixed;
  re['R'] = 0;
  re['P'] = 1;
  re['S'] = 2;
  cin >> n >> q >> s;
  vector<segTree> t(3, segTree(n));
  vector<fenwick> f(3, fenwick(n));
  for (int i = 0; i < n; i++)
    a[i] = re[s[i]], t[a[i]].upd(i, make_pair(i, i)), f[a[i]].upd(i, 1);
  cout << getAns(t, f) << '\n';
  while (q--) {
    int pos;
    char ch;
    cin >> pos >> ch;
    pos--;
    t[a[pos]].upd(pos, neu);
    f[a[pos]].upd(pos, -1);
    a[pos] = re[ch];
    t[a[pos]].upd(pos, make_pair(pos, pos));
    f[a[pos]].upd(pos, 1);
    cout << getAns(t, f) << '\n';
  }
}
