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#include <bits/stdc++.h>
#define fi first
#define sc second
#define pb push_back
#define rep(i,p,k) for(int i=(p);i<(k);++i)
#define forn(i,p,k) for(int i=(p);i<=(k);++i)
#define forr(i,k,p) for(int i=(k)-1;i>=(p);--i)
#define each(a,b) for(auto&a:b)
#define all(v)  begin(v), end(v)
#define RET(smth)   return void(cout<<(smth)<<'\n');
#define sz(v) (int)v.size()
using namespace std;
using pii = pair<int,int>;
using ll = long long;
using lll = __int128_t;
using Vi = vector<int>;
#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) ;
#endif
map<string, int> cnt;

void load(string & t, const char * s, int l) {
    if(!l) {
        ++cnt[t];
        return;
    }
    load(t, s+1, l-1);
    t += *s;
    load(t, s+1, l-1);
    t.pop_back();
}

int solve(string const & s) {
    cnt.clear();
    string t{};
    load(t, s.data(), sz(s));
    int r = 0;
    for(auto &[_, c] : cnt) if(c >= 2) r++;
    return r;
}

int main() {
#ifndef DEBUG
    cin.tie(0) -> sync_with_stdio(0);
#endif
    int n,q; cin >> n >> q;
    string s; cin >> s;
    cout << solve(s) << '\n';
    while(q--) {
        int i; char z; cin >> i >> z;
        s[i-1] = z;
        cout << solve(s) << '\n';
    }
    return 0;
}