poj 2381 Random Gap

#include<iostream>using namespace std;char lock[16000000];int main(){__int64 i,a,c,m,r0,temp;while(scanf("%I64d%I64d%I64d%I64d",&a,&c,&m,&r0)!=EOF){memset(lock,0,sizeof(lock));temp=r0;while(!lock[temp]){lock[temp]=1;temp=(a*temp+c)%m;}int flag=0,max=0,j;for(i=0;i<16000000;i++){if(lock[i]&&flag){if(j>max)max=j;j=1;}if(lock[i]&&flag==0){flag=1;j=1;}if(lock[i]==0&&flag)j++;}cout<<max<<endl;}return 0;}