#include "stdio.h" int prime(int n){//素數判斷     int i;     if(n>2 && !(n&1) || n<2)         return 0;     for(i=3;i*i<=n;i+=2)         if(!(n%i))             return 0;     return 1; } int main(int argv,char *argc[]){     int n,s,t;     printf("Input n(n<=500):");     if(scanf("%d",&n)!=1 || n<2 || n>500)     {         printf("Input error, exit...\n");         return 0;     }     for(t=s=0;t<10 && n>1;n--)         if(prime(n))         {             printf("%6d",n);             s+=n;             t++;         }     printf("\nsum=%d\n",s);     return 0; }