1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
#include <bits/stdc++.h>

using namespace std;

#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define ll long long
#define ld long double
ll mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;

const int N=200007;

ll DP[N][3];
int cnt[300];
int n,q;
int ile[300][2];

void get()
{
    int a=cnt['C'],b=cnt['Z'],c=cnt['N'];
    int p=(2*(c+b-a)%3+3)%3;
    int ans=DP[c][p];
    if(n>1&&n%2==1)
    {
        if(ile['C'][0]==0&&ile['Z'][1]==0) ans=(ans-1+mod)%mod;
        if(ile['Z'][0]==0&&ile['C'][1]==0) ans=(ans-1+mod)%mod;
    }
    cout<<ans<<endl;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>q;
    string s;
    cin>>s;
    DP[0][1]=1,DP[0][2]=1;
    for(int i=1;i<=n;i++)
    {
        for(int j=0;j<3;j++) DP[i][j]=(DP[i-1][j]+DP[i-1][(j+2)%3])%mod;
    }
    for(int i=0;i<n;i++)
    {
        cnt[s[i]]++;
        ile[s[i]][i%2]++;
    }
    get();
    while(q--)
    {
        int i;
        char c;
        cin>>i>>c;
        i--;
        cnt[s[i]]--;
        ile[s[i]][i%2]--;
        s[i]=c;
        cnt[s[i]]++;
        ile[s[i]][i%2]++;
        get();
    }


    return 0;
}