a+aa+aaa+aaaa+.......

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【Problem Description】

Seeking Sn = a + aa + aaa + ... + aa ... an value of a, where a is a number. For example: 2 + 22 + 222 + 22222 + 2222 (where n = 5), n input from the keyboard.

[Input form]

And enter a positive integer n, a is a positive integer less than 10. Two numbers separated by a space.

[Form] output

Output Sn = a + aa + aaa + ... + aa ... an a value of a.

[Sample input]

2 5

[Sample output]

24690

[Sample Description]

2+22+222+2222+22222=24690

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
	int a,n,b=0,c,Sn=0;
	cin>>a>>n;
	for(int i=1;i<=n;i++)
	{
		b=b+pow(10,i-1);  //pow函数为次方（x，y）即x的y次方
		c=b*a;
		Sn=Sn+c;
	}
	cout<<Sn;
	return 0;
}