poj 3652 Persistent Bits

#include <iostream>using namespace std;int A, B, C, S;int sovel(){ int x = S; int state = 0; int n = 1; while ( (x = (A * x + B) % C ) && x != S && n <= C) {  n ++;  state |= (x ^ S); } return state;}int main(){ int i; int state; while (scanf("%d", &A) && A) {  scanf("%d %d %d", &B, &C, &S);  state = sovel();  for (i = 1; i <= 16; i++)  {   if (state & (1 << (16 - i)))   {    printf("?");   }   else   {    if( S & (1 << (16 - i)) )     printf("1");    else     printf("0");   }  }  printf("n"); } return 0;}