//kadai08y 25D8104025H
#include<stdio.h>
#include<math.h>
int main(void){
int a,b,i,j,n,count,m,p[100000];
p[0]=0; p[1]=0;
for(i=2; i<100000; i++){
p[i]=1;
}
for(i=2; i<=m; i++){
if(p[i]!=0){
for(int j=2*i; j<100000; j+=i){
p[j]=0;}}}
for(i=2; i<n/2; i++){
if(p[i]!=0){
a=i;
b=n-a;
if(p[b]!=0){
count++;
}
}
}
return 0;}
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