krsu 804

/*
* by: senb1
*/
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <locale>
#include <numeric>
#include <cstring>
#include <cmath>

#include <deque>
#include <list>
#include <map>
#include <stack>
#include <string>
#include <vector>
#include <array>
#include <queue>
#include <set>

using namespace std;

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define yes cout << "YES\n"
#define no cout << "NO\n"
#define fr first
#define sc second
#define endl "\n"
#define ll long long
#define ull unsigned long long
#define ld long double
#define nl cout << "\n";

const ll maxn = 1e6 + 10;
const ll mod = 3e4;
const int inf = 1000000000;
const ull absmax = 1e18;
// 4294967296

ll binpow(ll a, ll b) {
    ll res = 1;
    while (b > 0) {
        if (b & 1)
            res = res * a % mod;
        a = a * a % mod;
        b >>= 1 % mod;
    }
    return res % mod;
}

ll divup(ll x, ll y) {
    return (x - 1) / y + 1;
}

ll gcd(ll a, ll b) {
    if (a % b == 0)
        return b;
    if (b % a == 0)
        return a;
    if (a > b)
        return gcd(a % b, b);
    return gcd(a, b % a);
}

ll lcm(ll a, ll b) {
    return (a * b) / gcd(a, b);
}

ld double_factorial(int n) {
    if (n == 0) {
        return 1;
    }
    else if (n == 1) {
        return n;
    }
    else if (n % 2 == 0) {
        return n * double_factorial(n - 2);
    }
    else {
        return n * double_factorial(n - 1);
    }
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    //cout << fixed << setprecision(12);
    //setlocale(LC_ALL, "RUS");

    string a, b;
    cin >> a >> b;

    while(a.size() < 9)
        a = '0' + a;
    while(b.size() < 9)
        b = '0' + b;

    int res = 0;
    bool fl = 0;
    for (int i = a.size() - 1; i >= 0; i--) {
        int num1 = a[i] - '0', num2 = b[i] - '0', c = 0;
        c = num1 + num2;
        if (fl)
            c = c + 1;
        if (c > 1) {
            res++;
            fl = 1;
        }
        else
            fl = 0;

    }

    cout << res;

}