Friends Pairing Solutions

Friend Pairing Solutions

class Solution
{
       public long countFriendsPairings(int n) 
    { 
       //code here
       long a=1,b=1,c=1,mod=1000000007;
       for(int i=2;i<=n;i++){
           c=((b%mod)+(((i-1)%mod)*(a%mod))%mod)%mod;
           a=b;
           b=c;
       }
       return c;
    }
}