#include"bits/stdc++.h"
#define rep(i,n) for(ll i=0;i<n;++i)
#define ALL(x) x.begin(),x.end()
#define MOD 1000000007
#define INF INT_MAX
#define FLOAT_ANS setprecision(10)
#define elif else if
// #define input(type,n) type n;cin>>n

using namespace std;
typedef long long ll;
typedef unsigned long long ull;

//最大公約数
template<typename T>
T gcd(T a, T b) {
	if (a % b == 0) {
		return(b);
	}
	else {
		return(gcd(b, a % b));
	}
}

//最小公倍数
template<typename T>
T lcm(T a, T b) {
	return a / gcd(a, b) * b;
}

bool isLarger(string s,string t){
	/*SのほうがTより大きければtrue*/
	rep(i,min(s.length(),t.length())){
		if(s[i]>t[i]){
			return true;
		}
		if(s[i]<t[i]){
			return false;
		}
	}

	if(s.length()>t.length()){
		return true;
	}
	else{
		return false;
	}
}

ll f(ll k){
	string s=to_string(k);
	ll ans=0;
	rep(i,s.length()){
		ll j=s[i]-'0';
		ans+=pow(k,s.length()-i-1)*j;
	}

	return ans;
}

int main(void){
	string a,b;
	cin>>a>>b;
	ll a_=0;
	ll b_=0;
	for(char c:a){
		a_+=c-'0';
	}
	for(char c:b){
		b_+=c-'0';
	}

	cout<<max(a_,b_);
}


/*

*/

//#include<bits/stdc++.h>
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string.h>
#include <vector>
#include <utility>
#include <map>

//#pragma GCC optimize "trapv"

//#define int long long
#define For(i,a,b) for(int  i=a;i<b;i++)

#define pb push_back
#define endl "\n"

#define F first
#define S second

#define dracarys ios_base::sync_with_stdio(false);cin.tie(NULL)
#define all(v) v.begin(),v.end()

#define TEST_CASE int  t;cin>>t;while(t--)
#define debug(...) cout<<#__VA_ARGS__<<" = "; print(__VA_ARGS__);

using namespace std;
const int MOD = 1e9 + 7;

void print()  {    cout<<endl;  }
void printArray()  {    return;  }
void read() { return; }

template<typename T , typename... Args>  void print(T a , Args... arg)    {    cout << a << " " ;    print(arg...);    }

template<typename T , typename... Args> void read(T &a , Args&... arg) {   cin >> a;   read(arg...);   }

template<typename T,typename... Args> void read(vector<T>&v , Args&... arg) {  for(auto &i : v)  cin>>i;  read(arg...);  }

template<typename T,typename... Args> void printArray(vector<T>&v, Args&... arg) {   for(auto i : v)     cout<<i<<" ";   cout<<endl;  printArray(arg...);    }

int power(int a,int b) { int  res=1; while(b) { if(b&1LL) res=res*a; b>>=1LL; a=a*a; } return res; }

int modPower(int a,int b) { int res=1; while(b) { if(b&1L) res=(res%MOD*a%MOD)%MOD; b>>=1; a=(a%MOD*a%MOD)%MOD; } return res; }

int gcdExtended(int a,int b,int *x,int *y){ if(a==0) { *x=0,*y=1; return b; } int x1,y1; int gcd=gcdExtended(b%a,a,&x1,&y1); *x=y1-(b/a)*x1; *y = x1; return gcd; }

int modInverse(int b,int m) {int x,y; int g=gcdExtended(b,m,&x,&y); if (g != 1) return -1; return (x%m + m) % m; }

int modDivide(int a,int b,int m=MOD) { a=a%m; int inv=modInverse(b,m); if(inv==-1) return -1; else return (inv*a)%m; }


void runCase_()
{
        string a,b; read(a,b);
        int s1 = 0,s2 = 0;
        for(char c : a) s1 += (c - '0');
        for(char c : b) s2 += (c - '0');
        if(s1 > s2) print(s1);
        else print(s2);
}


signed main()
{
     dracarys;
//      TEST_CASE
     runCase_();
     return 0;
}

/** TEST CASES HERE **/
/*

*/
