孪生素数

#include <stdio.h>#include <math.h>#include <assert.h>int is_prime(int x){int i,m;assert(x>=0);if(x==1)return 0;m=floor(sqrt(x)+0.5);for(i=2;i<=m;i++){if(x%i==0)return 0;}return 1;}int main(){int i,m;scanf("%d",&m);for(i=m-2;i>=3;i--){if(is_prime(i)&&is_prime(i+2)){printf("%d %d\n",i,i+2);break;}}return 0;}