#include <bits/stdc++.h>

using namespace std;

ifstream in("test.in");
ofstream out("test.out");


int main() {
    int sum = 0;
    char prevSymbol = '+';
    for (char symbol; in >> symbol;) {
        if (symbol == prevSymbol) {
            cout << "error" << endl;
            return 0;
        }
        if (symbol != '+') {
            sum += symbol - '0';
        }
        prevSymbol = symbol;
    }
    cout << sum << endl;

    return 0;
}