rt，代码如下

#include<bits/stdc++.h>
using namespace std;
int x,num[15],len=0,ans=0;
char c;
int main()
{
	cin>>x;
	c=getchar();
	c=getchar();
	while(('0'<=c&&c<='9')||('A'<=c&&c<='Z'))
	{
		if('A'<=c&&c<='Z')
			c='9'+(c-'A')+1;
		num[++len]=c-'0';
		c=getchar();
	}
	int w=1;
	for(int i=len;i>=0;i--)
	{
		ans+=num[i]*w;
		w*=x;
	}
	cout<<ans;
	return 0;
}