Untitled

#include <iostream>
#include <vector>

using namespace std;
int n,q;
string s;
vector<vector<int>> tree;
vector<int> a(26,0);
vector<int> change;

int binpow (int a, int n) {
	int res = 1;
	while (n) {
		if (n & 1)
			res *= a;
		a *= a;
		n >>= 1;
	}
	return res;
}

void next(int c,int v){
    int r;
    vector<int> a2(26,0);
    for (int i=0;i<r;i++){
        r=(c+i)%26;
        a2[r]=tree[v][i];
    }
    tree[v]=a2;
}

void push(int v, int tl, int tr)
{
    if (!change[v]){
        return;
    }
    if (tl==tr-1){
        next(change[v],v);
        return;
    } else{
        change[2 * v] = change[v];
        change[2 * v + 1] = change[v];
        next(change[v],v);
        change[v]=0;
    }
}

int res(vector<int> &a){
    long long ans=1;
    for (int i=0;i<26;i++){
        ans+=bool(a[i]!=0);
    }
    for (int i=0;i<26;i++){
        if (a[i]>0){
            ans*=binpow(2,a[i]-1);
            ans%=1000000007;
        }
    }
    return (ans-1)%1000000007;
}

void build (int v, int tl, int tr) {
	if (tl == tr)
		tree[v][s[tl]-'a'] = 1;
	else {
		int tm = (tl + tr) / 2;
		build (v*2, tl, tm);
		build (v*2+1, tm+1, tr);
		vector<int> a2(26);
		for (int i=0;i<26;i++){
		    a2[i]=tree[v*2][i]+tree[v*2+1][i];
		}
		tree[v] = a2;
	}
}

vector<int> get(int l, int r, int v, int tl, int tr) {
	if (l <= tl && tr <= r) {
        return tree[v];
    }
    if (tr < l || r < tl) {
        return a;
    }
	push(v, tl, tr);
    int tm = (tl + tr) / 2;
         
	vector<int> a2 = get(l, r, v * 2,     tl,     tm);
	vector<int> a3=get(l, r, v * 2 + 1, tm + 1, tr);
	for (int i=0;i<26;i++){
	    a2[i]+=a3[i];
	}
	return a2;
}

void upd(int l, int r, int c, int v, int tl, int tr) {
    if (l <= tl && tr <= r) {
        next(c,v);
        return;
    }

    if (tr < l || r < tl) {
        return;
    }

    push(v,tl,tr);   
    int tm = (tl + tr) / 2;
    upd(l, r, c, v * 2,     tl,     tm);
    upd(l, r, c, v * 2 + 1, tm + 1, tr);
    
    vector<int> a2(26,0);
	for (int i=0;i<26;i++){
	    a2[i]=tree[v*2][i]+tree[v*2+1][i];
	}
	tree[v] = a2;
}

int main(){
    cin>>n>>q;
    cin>>s;
    for (int i=0;i<4*n;i++){
        tree.push_back(a);
        change.push_back(0);
    }
    build(1,0,n-1);
   
    int p,l,r,k;
    for (int i=0;i<q;i++){
        cin>>p;
        if (p==2){
            cin>>l>>r;
            vector<int> t=get(l,r,1,0,n-1);
            cout<<res(t)<<endl;
        }else{
            cin>>l>>r>>k;
            for (int j=l;j<r+1;j++){
                change[j]=k;
            }
            upd(l, r, k, 1, 0, n-1);
        }
        //for (int ii=0;ii<4*n;ii++){
            //for (int jj=0;jj<26;jj++){
                //cout<<"vertex "<<ii<<" letter "<<jj<<" count "<<tree[ii][jj]<<endl;
            //}
        //}
    }
    return 0;
}