【C】求Sn=a+aa+aaa+aaaa+aaaaa的前5项之和

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
int n = 0;
int i = 0;
int sum = 0;
int a[10] = { 0 };
scanf("%d", &n);
a[0] = n;
for (i = 1; i < 5; i++)
{
a[i] = a[i - 1] * 10 + a[0];
}
for (i = 0; i < 5; i++)
{
sum += a[i];
}
printf("%d\n", sum);
system("pause");
return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
int a = 5;
int n = 5;
int sum = 0;
int i = 0;
int ret = 0;

for(i=0; i<n; i++)
{
ret = ret*10 + a;
sum += ret;
}
printf("%d\n", sum);
system("pause");
return 0;
}