#include<bits/stdc++.h>
using namespace std;

#define V vector
#define pb push_back

typedef long long LL;
typedef pair<int, int> pi;

const int MN = 5e5 + 120;

//d r m f s l t
const int INF = 2e9 + 1000;

struct info {
    array<array<int, 3>, 8> tab;
    info() {
        for(auto& a0 : tab) {
            for(auto &y : a0) y = 0;
        }
    }
}i0;

void upd(array<int, 3> &a, array<int, 3> b) {
    if(a[1] == 0) {
        a = b;
        return;
    }
    if(a[1] <= b[1]) return;
    a = b;
}

void show(info i) {
    cout << "show" << endl;
    for(auto a8 : i.tab) {
        for(auto y : a8) cout << y << " ";
        cout << endl;
    }
}

info operator+ (const info & a, const info & b) {
    if(a.tab[0][0] == -1) return b;
    info c;
    
    // show(c);
    // show(a), show(b);
    for(int i = 0; i <= 7; i++) {
        auto [acost, apos, ares] = a.tab[i];
        // auto [acost, apos, ares] = b.tab[i];
        for(int j = 0; j <= 7; j++) {
            if(!(ares >> j & 1)) {
                continue;
            }
            auto [bcost, bpos, bres] = b.tab[j];
            if(bpos == INF) {
                upd(c.tab[i], array<int, 3>{acost, apos, ares | bres});
            } else {
                upd(c.tab[i], array<int, 3>{acost + bcost, min(apos, bpos), bres});
            }
        }
    }
    // show(c);
    return c;
}

info seg[MN * 4];

void pull(int x) {
    seg[x] = seg[x * 2] + seg[x * 2 + 1];
}


void modify(int x, int l, int r, int p, const info &i) {
    if(l == r) {
        seg[x] = i;
        return;
    }
    int mid = l + r >> 1;
    if(p <= mid) modify(x * 2, l, mid, p, i);
    else modify(x * 2 + 1, mid + 1, r, p, i);
    pull(x);
}


info query(int x, int l, int r, int ql, int qr) {
    // cout << "l , r" << l << " " << r << endl;
    if(ql <= l && qr >= r) {
        return seg[x];
    }
    int mid = l + r >> 1;
    auto ans = i0;
    if(ql <= mid) ans = ans + query(x * 2, l, mid, ql, qr);
    if(qr >= mid + 1) ans = ans + query(x * 2 + 1, mid + 1, r, ql, qr);
    return ans;
}

map<char, int> mp;

info get_info(char c, int pos) {
    info in;
    if(mp[c] < 0) {
        int x = -mp[c];
        for(int j = 0; j <= 7; j++) {
            in.tab[j][1] = INF;
            in.tab[j][2] = (1 << j) | (1 << x) | 1;
        }
    } else if(mp[c] > 0) {
        int x = mp[c];
        for(int j = 0; j <= 7; j++) {
            if(1 << j & x) {
                in.tab[j][0] = 1;
                in.tab[j][1] = pos;
                in.tab[j][2] = 1;
            } else {
                in.tab[j][0] = 0;
                in.tab[j][1] = INF;
                in.tab[j][2] = 1 | 1 << j;
            }
        }
    } else {
        for(int j = 0; j <= 7; j++) {
            in.tab[j] = {0, INF, 1 | 1 << j};
        }
    }
    // for(auto a8 : in.tab) {
    // }
    return in;
}

void build(int x, int l, int r, string & s) {
    if(l == r) {
        seg[x] = get_info(s[l], l);
        return;
    }
    int mid = l + r >> 1;
    build(x * 2, l, mid, s), build(x * 2 + 1, mid + 1, r, s);
    pull(x);
}   

void solve() {
    int n, q; cin >> n >> q;
    string s; cin >> s;
    s = " " + s;
    // s = " symphony";
    
    build(1, 1, n, s);
    // cout << query(1, 1, n, 2, 2).tab[0][0] << endl;
    // show(query(1, 1, n, 1, 1));
    // show(query(1, 1, n, 1, 2));
    // show(query(1, 1, n, 1, 5));
    // show(query(1, 1, n, 1, 6));
    // show(query(1, 1, n, 5, 6));
    // cout << query(1, 1, n, 3, 4).tab[0][0] << endl;
    // show(query(1, 1, n, 3, 3));
    // show(query(1, 1, n, 4, 4));
    // show(query(1, 1, n, 3, 4));
    // cout << query(1, 1, n, 2, 4).tab[0][0] << endl;
    // cout << query(1, 1, n, 3, 4).tab[0][1] << endl;


    // for(int i = 3; i <= 4; i++) show(query(1, 1, n, i, i));
    for(int i = 1; i <= q; i++) {
        char t; cin >> t;
        // cout << "i : " << i << endl;
        // for(int i = 1; i <= n; i++) {
        //     show(query(1, 1, n, i, i));
        // }
        if(t == '#') {
            int i, j; cin >> i >> j;
            string s; cin >> s;
            for(int t = i; t <= j; t++) {
                modify(1, 1, n, t, get_info(s[t - i], t));
            }
        } else {
            int i, j; cin >> i >> j;
            cout << (j - i + 1) - 2 * query(1, 1, n, i, j).tab[0][0] << "\n";
        }
    }
}


int main() {
    i0.tab[0][0] = -1;
    mp['d'] = -1;
    mp['r'] = -2;
    mp['m'] = -3;
    mp['f'] = -4;
    mp['s'] = -5;
    mp['l'] = -6;
    mp['t'] = -7;
    mp['o'] = 2 + 32;
    mp['e'] = 4;
    mp['i'] = 8 + 128;
    mp['a'] = 16 + 64;

    ios::sync_with_stdio(0), cin.tie(0);
    solve();
}