# INOI 2015 Periodic strings Problem

Can anyone tell me if my solution to the Periodic Strings problem from INOI 2015 is correct please? I can’t test it anywhere.

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Here is the official test data from last year’s INOI.

https://www.dropbox.com/s/0wn5pt9y9cm601w/PeriodicStrings-fulldata.zip?dl=0&preview=PeriodicStrings-fulldata.zip

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Thank you!!!

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i have a problem with this question… i dont see why this soltution of mine is wrong

``````#include<bits/stdc++.h>

using namespace std;

long long int power(int x,int a,int d)
{

int i=0,b[1024],m,n;
long long int ans=1;

while(a!=0)
{
b[i]=a%2;
a=a/2;
i++;
}
n=i;
for (int i=0;i<n;i++)
{
if (b[i]==1)
{
ans=((ans%d)*(x%d))%d;
}
x=((x%d)*(x%d))%d;
}

return ans;
}

const long long int N=1e5+5;

long long int dp[N];

int main()
{
long long int n,m,a=0;
cin>>n>>m;
dp[1]=1;
for(int i=1; i<=n;i++)
{
for(int j=1;j<i;j++)
{
if(i%j==0)
{
a=(a+dp[j])%m;-
}
}
dp[i]=(power(2,i,m)-a)%m;
a=0;
}
cout<<dp[n]%m<<endl;
return 0;
}
``````
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