#include <bits/stdc++.h>
using namespace std;
using cd = complex<double>;
double pi = acos(-1);
int n, m;
vector<cd> va, vb;
string s;
void fft(vector<cd>&arr, bool mode) {
int cn = arr.size();
if(cn == 1) return;
vector<cd> a0, a1;
for(int i=0;i<cn;i+=2) {
a0.push_back(arr[i]);
a1.push_back(arr[i+1]);
}
fft(a0, mode); fft(a1, mode);
double ang = (mode ? -1 : 1) * 2*pi/cn;
cd croot(1), w(cos(ang), sin(ang));
for(int i=0;i<cn/2;i++) {
arr[i] = a0[i] + croot * a1[i];
arr[i+cn/2] = a0[i] - croot * a1[i];
croot *= w;
}
if(mode) for(auto &e:arr) e /= 2;
}
int main() {
cin.tie(0) -> sync_with_stdio(0);
cin >> n >> m;
va.resize(n);
vb.resize(m);
cin >> s; reverse(s.begin(), s.end());
for(int i=0;i<n;i++) va[i] = s[i] - '0';
cin >> s; reverse(s.begin(), s.end());
for(int i=0;i<m;i++) vb[i] = s[i] - '0';
if(n < m) {swap(n, m); swap(va, vb);}
va.push_back(0);
while(vb.size() < va.size()) vb.push_back(0);
while(__builtin_popcount(va.size()) > 1) {va.push_back(0); vb.push_back(0);}
va.push_back(0); vb.push_back(0);
while(__builtin_popcount(va.size()) > 1) {va.push_back(0); vb.push_back(0);}
fft(va, 0); fft(vb, 0);
for(int i=0;i<va.size();i++) va[i] *= vb[i];
fft(va, 1);
vector<int> ans;
int curcar = 0;
for(auto &e:va) {
curcar += round(e.real());
ans.push_back(curcar%10);
curcar /= 10;
}
while(!ans.empty() && ans.back() == 0) ans.pop_back();
reverse(ans.begin(), ans.end());
for(auto &e:ans) cout << e;
if(ans.empty()) cout << 0;
}
