poj 2406 Power Strings

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
#define N 1000009
char s[N];
int next[N];
int l;
void getnext()
{
    l=strlen(s);
    next[0]=-1;
    for(int i=1,j;i<l;i++)
    {
        j=next[i-1];
        while(s[i]!=s[j+1]&&j>=0)
        j=next[j];
        next[i]=s[i]==s[j+1]?j+1:-1;
    }
    if(l%(l-next[l-1]-1)==0)
    printf("%d\n",l/(l-next[l-1]-1));
    else
    printf("%d\n",-1);
}
int main()
{
    while(scanf("%s",s))
    {
        getnext();
    }
    return 0;
}