10268 - 498'

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
using namespace std;

int main(){
	int x=0;

	while(scanf("%d",&x)!= EOF){
		getchar();
		int temp = 0;
		int p[1000] ={0};
		int pc = 0;
		long long int sum = 0;
		while(scanf("%d",&p[pc])){
			pc++;
			if(getchar() =='\n'){
			
				break;
			}
		
		}
		for(int i= 0 ; i < pc ; i++){
			sum+= p[i]*(pc-i-1)*pow(x,pc-i-2);
		}
		
		cout << sum<<endl;
		
	}

}