#include <iostream>
#include <string>
using namespace std;
typedef unsigned long long int ull;
string a,b;
ull r;
string ll_max = "9223372036854775807";
int main() {
cin >> a >> b >> r;
if(a=="0" || b=="0") cout<<0;
else if(a.length()>=20 || b.length() >=20 || a.compare(ll_max)>0 || b.compare(ll_max) >0) cout<<"overflow";
else {
ull A = stoll(a);
ull B = stoll(b);
if(B > r/A) cout<<"overflow";
else cout<< A*B;
}
}