#include <bits/stdc++.h>

struct Matrix{
    int v[5][5];
    Matrix(){
        for (int i = 0; i < 5; i++){
            for (int j = 0; j < 5; j++){
                v[i][j] = 1e9;
            }
            v[i][i] = 1;
        }
    }

    int *operator[](int i){
        return v[i];
    }
};

Matrix operator*(Matrix a, Matrix b){
    Matrix c;
    for (int i = 0; i < 5; i += 1) {
        c[i][i] = 1e9;
    }
    for (int i = 0; i < 5; i++){
        for (int k = 0; k < 5; k++){
            for (int j = 0; j < 5; j++){
                c[i][j] = std::min(c[i][j], a[i][k] + b[k][j]);
            }
        }
    }
    return c;
}

Matrix get_mat(char c) {
    Matrix res;
    if(c == 'd' or c == 's') {
        res[0][1] = 0;
    }
    if (c == 'r') {
        res[0][2] = 0;
    }
    if (c == 'm' or c == 't') {
        res[0][3] = 0;
    }
    if(c == 'f' or c == 'l') {
        res[0][4] = 0;
    }
    if (c == 'o') {
        res[1][0] = 0;
    }
    if(c == 'e') {
        res[2][0] = 0;
    }
    if (c == 'i') {
        res[3][0] = 0;
    }
    if (c == 'a') {
        res[4][0] = 0;
    }
    return res;
}

const int maxn = 5e5 + 233;
Matrix tree[maxn << 2], dp[maxn];
#define ls o << 1
#define rs o << 1 | 1

void build(int o, int l, int r) {
    if(l == r) {
        tree[o] = dp[l];
        return;
    }
    int mid = (l + r) >> 1;
    build(ls, l, mid);
    build(rs, mid + 1, r);
    tree[o] = tree[ls] * tree[rs];
}

void modify(int o, int l, int r, int pos, Matrix v) {
    if(l == r) {
        tree[o] = v;
        return;
    }
    int mid = (l + r) >> 1;
    if(pos <= mid) {
        modify(ls, l, mid, pos, v);
    }
    else {
        modify(rs, mid + 1, r, pos, v);
    }
    tree[o] = tree[ls] * tree[rs];
}

Matrix query(int o, int l, int r, int ql, int qr) {
    if(ql <= l and r <= qr) {
        return tree[o];
    }
    int mid = (l + r) >> 1;
    Matrix res;
    if(ql <= mid) {
        res = query(ls, l, mid, ql, qr);
    }
    if(qr > mid) {
        res = res * query(rs, mid + 1, r, ql, qr);
    }
    return res;
}

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    int n, q;
    std::string s;
    std::cin >> n >> q;
    std::cin >> s;
    for (int i = 0; i < n; i += 1) {
        dp[i + 1] = get_mat(s[i]);
    }
    build(1, 1, n);
    // auto cc = dp[1] * dp[2];
    // for (int i = 0; i < 5; i += 1) {
    //     for (int j = 0; j < 5; j += 1) {
    //         std::cout << dp[1][i][j] << ' ';
    //     }
    //     std::cout << '\n';
    // }
    build(1, 1, n);
    for (int i = 0; i < q; i++){
        int l, r;
        std::string p, t;
        std::cin >> p >> l >> r;
        if (p == "#") {
            std::cin >> t;
            for (int i = l; i <= r; i += 1) {
                modify(1, 1, n, i, get_mat(t[i - l]));
            }
        }
        else {
            std::cout << query(1, 1, n, l, r)[0][0] << '\n';
        }
    }
  
    return 0;
}