poj 3370 Halloween treats

#include<iostream>#include<cstdlib>#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>using namespace std;int a[100000] , mod[100000] ;int main(){    int c , n ;    while ( scanf("%d%d",&c,&n) , c || n )    {        int i , j ;        for ( i = 0 ; i < n ; i ++ ) scanf("%d",&a[i]) , mod[i] = -2 ;        mod[0]=-1 ;        __int64 sum = 0 ;        for ( i = 0 ; i < n ; i ++ )        { sum += a[i] ; if ( mod [ sum % c ] != -2 ) {     for ( j = mod [ sum % c ] + 1 ; j <= i ; j ++ )     {         cout<<j+1;         if ( i != j )  cout<<' ';     }     cout<<endl;     break; } mod [sum%c] = i ;        }    }    return 0;}