Multiple of 11

#include<iostream>
#include<algorithm>
using namespace std;
int main(){
	string numero = "";
	while(cin >> numero && numero != "0"){
		int tam = numero.size();
		int sumpar = 0,sumimpar = 0;
		for(int i = 0; i < tam; i++){
			if(i % 2 == 0) sumimpar += numero[tam - i - 1] - 48;
			else sumpar += numero[tam - i - 1] - 48;
		}
		if((sumimpar - sumpar) % 11 == 0) cout << numero << " is a multiple of 11." << endl; 
		else cout << numero << " is not a multiple of 11." << endl; 
	}
	return 0;
}