TLE70分求调

#include<bits/stdc++.h>

using namespace std;
const int N = 1e6+10;
#define int long long
int nxt[N],f[N];
signed main(){
    ios::sync_with_stdio(0);
	cin.tie(0);
    int m;
    cin>>m;
    string s2;
    cin>>s2;
    s2 = " "+s2;
    for(int i = 2,j = 0;i<=m;i++){
        while(j && s2[i]!=s2[j+1]) j = nxt[j];
        if(s2[i]==s2[j+1]) j++;
        nxt[i] = j;
    }
    long long j = 0,cnt = 0;
    for(int i = 1;i<=m;i++){
        j = i;
        while(nxt[j]) j = nxt[j];
        if(nxt[j]) nxt[i] = j;
        cnt+=i-j;
    }
    cout<<cnt;

    return 0;
}