//#pragma GCC optimize("O3,unroll-loops,inline")

#include <bits/stdc++.h>

using namespace std;

vector<string> note = {"do", "re", "mi", "fa", "so", "la", "ti"};

struct node {
    int dp[8][8];

    node() {
        for (auto &i: dp)
            for (int &j: i)
                j = -1000000;
    }

    node(char ch) {
        for (auto &i: dp)
            for (int &j: i)
                j = -1000000;
        dp[7][7] = 0;
        for (int i = 0; i < 7; ++i) {
            if (ch == note[i][1])
                dp[i][7] = 0;
            if (ch == note[i][0])
                dp[7][i] = 0;
        }
    }
};

node operator+(node a, node b) {
    node c;
    for (int i = 0; i < 8; ++i)
        for (int j = 0; j < 8; ++j) {
            c.dp[i][j] = max(c.dp[i][j], a.dp[i][j]);
            c.dp[i][j] = max(c.dp[i][j], b.dp[i][j]);
        }
    for (int k = 0; k < 8; ++k)
        for (int i = 0; i < 8; ++i)
            for (int j = 0; j < 8; ++j)
                c.dp[i][j] = max(c.dp[i][j], a.dp[i][k] + b.dp[k][j] + 2 * (k < 7));
    return c;
}

const int N = 5e5;

node tr[2 * N];

signed main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, q;
    cin >> n >> q;
    string s;
    cin >> s;
    for (int i = 0; i < n; ++i) {
        tr[i + n] = node(s[i]);
    }
    for (int i = n - 1; i; --i) tr[i] = tr[i << 1] + tr[i << 1 | 1];
    while (q--) {
        char t;
        cin >> t;
        if (t == '?') {
            int l, r;
            cin >> l >> r;
            int len = r - l + 1;
            --l, --r;
            node left, right;
            for (l += n, r += n; l <= r; l >>= 1, r >>= 1) {
                if (l & 1) left = left + tr[l++];
                if (~r & 1) right = tr[r--] + right;
            }
            node res = left + right;
            int ans = 0;
            for (auto &i: res.dp)
                for (int j: i)
                    ans = max(ans, j);
            cout << len - ans << '\n';
        } else {
            int l, r;
            cin >> l >> r;
            --l, --r;
            string ns;
            cin >> ns;
            for (int i = l; i <= r; ++i) {
                tr[i + n] = node(ns[i - l]);
                for (int j = i + n; j > 1; j >>= 1, tr[j] = tr[j << 1] + tr[j << 1 | 1]);
            }
        }
    }
}