#include <bits/stdc++.h>
using namespace std;
const int INF = 10000000;
array<array<int, 5>, 5> e(){
  array<array<int, 5>, 5> ans;
  for (int i = 0; i < 5; i++){
    for (int j = 0; j < 5; j++){
      if (i == j){
        ans[i][j] = 0;
      } else {
        ans[i][j] = INF;
      }
    }
  }
  return ans;
}
array<array<int, 5>, 5> make(char c){
  array<array<int, 5>, 5> ans;
  for (int i = 0; i < 5; i++){
    for (int j = 0; j < 5; j++){
      ans[i][j] = INF;
    }
  }
  for (int i = 0; i < 5; i++){
    ans[i][i] = 1;
  }
  if (c == 'a'){
    ans[0][1] = 0;
  }
  if (c == 'e'){
    ans[0][2] = 0;
  }
  if (c == 'i'){
    ans[0][3] = 0;
  }
  if (c == 'o'){
    ans[0][4] = 0;
  }
  if (c == 'f' || c == 'l'){
    ans[1][0] = 0;
  }
  if (c == 'r'){
    ans[2][0] = 0;
  }
  if (c == 'm' || c == 't'){
    ans[3][0] = 0;
  }
  if (c == 'd' || c == 's'){
    ans[4][0] = 0;
  }
  return ans;
}
array<array<int, 5>, 5> op(array<array<int, 5>, 5> L, array<array<int, 5>, 5> R){
  array<array<int, 5>, 5> ans;
  for (int i = 0; i < 5; i++){
    for (int j = 0; j < 5; j++){
      ans[i][j] = INF;
      for (int k = 0; k < 5; k++){
        ans[i][j] = min(ans[i][j], L[i][k] + R[k][j]);
      }
    }
  }
  return ans;
}
struct segment_tree{
  int N;
  vector<array<array<int, 5>, 5>> ST;
  segment_tree(string s){
    int n = s.size();
    N = 1;
    while (N < n){
      N *= 2;
    }
    ST.resize(N * 2 - 1);
    for (int i = 0; i < n; i++){
      ST[N - 1 + i] = make(s[i]);
    }
    for (int i = n; i < N; i++){
      ST[N - 1 + i] = e();
    }
    for (int i = N - 2; i >= 0; i--){
      ST[i] = op(ST[i * 2 + 1], ST[i * 2 + 2]);
    }
  }
  void update(int i, char c){
    i += N - 1;
    ST[i] = make(c);
    while (i > 0){
      i = (i - 1) / 2;
      ST[i] = op(ST[i * 2 + 1], ST[i * 2 + 2]);
    }
  }
  int query(int L, int R){
    L += N - 1;
    R += N - 1;
    array<array<int, 5>, 5> l = e(), r = e();
    while (L < R){
      if (L % 2 == 0){
        l = op(l, ST[L]);
        L++;
      }
      if (R % 2 == 0){
        R--;
        r = op(ST[R], r);        
      }
      L = (L - 1) / 2;
      R = (R - 1) / 2;
    }
    return op(l, r)[0][0];
  }
};
int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, q;
  cin >> n >> q;
  string s;
  cin >> s;
  reverse(s.begin(), s.end());
  segment_tree ST(s);
  for (int i = 0; i < q; i++){
    char c;
    cin >> c;
    if (c == '?'){
      int a, b;
      cin >> a >> b;
      a--;
      cout << ST.query(n - b, n - a) << '\n';
    }
    if (c == '#'){
      int a, b;
      string t;
      cin >> a >> b >> t;
      a--;
      for (int j = 0; j < b - a; j++){
        ST.update(n - 1 - (a + j), t[j]);
      }
    }
  }
}