#include #include #include #include #include #include #include #include #include #include #include #include #include #define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl; #define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl; template inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } using namespace std; typedef long long ll; template vector> vec2d(int n, int m, T v){ return vector>(n, vector(m, v)); } template vector>> vec3d(int n, int m, int k, T v){ return vector>>(n, vector>(m, vector(k, v))); } template void print_vector(vector v, char delimiter=' '){ if(v.empty()) { cout << endl; return; } for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter; cout << v.back() << endl; } void test(){ int m = 625; map cnt; for(int x = 0; x < m; x++){ int y = (x*x)%m; if(cnt.count(y)) cnt[y]++; else cnt[y] = 1; } for(auto [x, c]: cnt) cout << x << ":" << c << " "; cout << endl; } const ll N = 1<<29; int main(){ ios::sync_with_stdio(false); cin.tie(0); cout << setprecision(10) << fixed; // test(); ll n, e; cin >> n >> e; ll x = 1; for(int i = 0; i < e; i++) x *= 5; if(e <= 4){ for(ll r = 0; r < x; r++){ ll d = abs(n-r*r); if(d%x == 0){ cout << r << endl; return 0; } } cout << "NaN" << endl; return 0; } const ll m = 625; ll rem = n%m; rem = (rem+m)%m; vector rr; for(int i = 0; i < m; i++){ if((i*i)%m == rem) rr.push_back(i); } for(ll i = 0; i*m < x; i++){ for(ll a: rr){ ll r = i*m+a; ll d = abs(n-r*r); if(d%x == 0){ if(n <= N){ cout << r << endl; return 0; } while(true){ n -= x; if(n >= -N){ if(n <= N){ cout << r << endl; return 0; } }else{ break; } } } } } cout << "NaN" << endl; return 0; }