#include <bits/stdc++.h>
#define loop(i, m, n) for(int i(m);i < n;i++)
#define pb push_back
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define DD(A) loop(i, 0, A.size())cout << A[i] <<" ";
#define in(x) cin >> x
#define clr(A, V) memset(A, V, sizeof(A))
#define ff first
#define ss second
#define readfile(X) freopen(X, "r", stdin)
#define writefile(X) freopen(X, "w", stdout)
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef vector<pii> vpii;
typedef pair<int, string> pis;
typedef pair<pair<int, int>, pair<int, int > > piiii;
int BASE = 1e9, sz1, sz2, i, j, carry;
string answer;
vi ans, anss;
void pre(vi &n1, vi &n2){
    int i, j, sz1 = (int)n1.size(), sz2 = (int)n2.size(), carry = 0;
}
void setLarge(vi &n1, vi &n2){
    if(sz1 < sz2) swap(n1, n2);
    else if(sz1 == sz2){
        bool big = 0, f = 1;
        for(int i = 0;i < sz1 && f;i++)
            if(n2[i] > n1[i]) f = 0, big = 1;
            else if(n1[i] > n2[i]) f= 0;
        if(big) swap(n1, n2);
    }
}
vi rev(vi &n1, vi &n2){
    for(int i = (int)n1.size()-1;i>=0;i--) n2.pb(n1[i]);
    return n2;
}
void stream1(vi &n, int &i){
    stringstream ss; string x;
    ss << n[i]; ss >>x;
    if(!i && n[i]) answer+=x;
    else x.insert(0, 9 - (int)x.size(), '0'), answer +=x;
}
void stream2(string &t, vi &n, int &c){
    int x;reverse(t.begin(), t.end());
    stringstream ss; ss << t; ss >> x;
    n.pb(x), t.clear(), c = 0;
}
vi setN(string s){
    vi n, rn;
    int c = 0;
    string t;
    for(int i = (int)s.size()-1;i>=0;i--){
        t+=s[i], c++;
        if(c == 9)
            stream2(t, n, c);
    }
    if(c)
        stream2(t, n, c);
    rn = rev(n, rn);
    return rn;
}
string print(vi &n){
    loop(i, 0, (int)n.size())
        stream1(n, i);
    return answer;
}
string add(vi &n1, vi &n2){
    pre(n1, n2);
    if(sz1 < sz2) swap(n1, n2);
    for(i = (int)n1.size()-1, j = (int)n2.size()-1;i >= 0; i--, j--)
        if(j>=0) ans.pb( (carry + n1[i] + n2[j] ) % BASE), carry = (carry + n1[i] + n2[j] ) / BASE;
        else ans.pb( (carry + n1[i]) % BASE), carry = (carry + n1[i]) / BASE;
    if(carry) ans.pb(carry); anss=rev(ans, anss);
    return print(anss);
}
string sub(vi &n1,vi  &n2){
    pre(n1, n2); setLarge(n1, n2);
        i = (int) n1.size()-1,  j = (int)n2.size()-1;
        for(;i >= 0; i--, j--)
            if(j >= 0)
                if(n1[i] - n2[j]-carry >= 0)ans.pb(n1[i] - n2[j]-carry), carry = 0;
                else n1[i] += BASE, ans.pb(n1[i] - n2[j]-carry), carry = 1;
            else ans.pb(n1[i]-carry), carry = 0; anss = rev(ans, anss);
    return print(anss);
}

int main() {
    string s1 = "520" , s2 = "20", o;
    vi n1 = setN(s1), n2 = setN(s2);
    o  = add(n1,n2);
    cout << o <<endl;
    return 0;
}