1 #include <iostream> 2 #include <cstdio> 3 #include <cmath> 4 using namespace std; 5  6 int k; 7  8 int main(){ 9     while(scanf("%d",&k)!=EOF){10         int q=sqrt(k*1.0);11         q++;12         bool flag=false;13         for(int l=2;l<=q;l++)14         if(k%l==0){15             flag=true;16             break;17         }18         if(!flag)19         printf("%d\n",k-1);20         else{21             for(int l=3;l<=k;l++)22             if(k%l==0){23                 printf("%d\n",l-1);24                 break;25             }26         }27     }28     return 0;29 }