//3.求和：n+nn+nnn+nnnn+nnnnn

#include<stdio.h>
int main()
{
int n = 0;
int num = 0;
int sum = 0;
  printf("n=");
scanf("%d", &n);
int i = 0;
for (i = 1; i <= 10000; i *= 10)
{
num += i*n;
sum += num;
}
printf("sum=%d", sum);
system("pause");
return 0;
}