/* Program1 */
#include<stdio.h>
main()
{
int n,sum;
[ 1 ];
n = 1;
while([ 2 ]){
sum = sum+n;
printf("%d: %d\n",n,sum);
[ 3 ];
}
}


这里的3填啥？ 1应该是sum=0 2应该是n<=50 3呢？