#include <iostream>
#include <string>
using namespace std;
int main()
{
int x;
cin >> x;
float result = 0;
char ss;
cin >> ss;
int y;
cin >> y;
while(ss!='x'){
if (y == 0) {
cout << "error";
break;
}
switch (ss)
{
case('+'):
result = x + y;
cin >> ss;
if (ss == 'x') {
cout << result << endl;
}
break;
case('-'):
result = x - y;
if (ss == 'x') {
cout << result << endl;
}
break;
case('/'):
result = float(x) / y;
if (ss == 'x') {
cout << result << endl;
}
break;
case('*'):
result = x * y;
if (ss == 'x') {
cout << result << endl;
}
break;
default:
break;
}
if (ss == '@') {
x = result;
cin >> ss;
cin >> y;
}
}
}