//in ra tat ca cac so nguyen to nho hon n duoc nhap tu ban phim
#include <stdio.h>
int i,n,k,dem,tong=0;
void main()
{
do
{
printf("nhap vao so nguyen to n : ");
scanf("%d",&n);
}while (n<=1 || n>=100);
for(k=1;k<=n;k++){
dem = 0;
for (i=1;i<=k;i++)
if(k%i==0)
dem++;
if (dem==2 && k!=2)
{
printf("cac so nguyen to nho hon n : %d\n",k);
tong=tong+k;
}
}
printf(" Tong cac so nho hon n la : %d\n",tong);
}
Cach 2:
/*void main(){
int kq=0,n;
scanf("%d",&n);
for(int i=n;i>2;i--){
int flag=1;
for(int j=i-1;j>1;j--){
if(i%j==0){
flag=0;
break;
}
}
if(flag)
{
printf("%d\n",i);
kq+=i;
}
}
printf("kq:%d",kq);
}*/