#include<iostream>
using namespace std;
int main() {
long long N, M, S;
cin >> M >> N;
if (M < 0 || M > 1000000000000){
return 0;
}
else if (N < 1 || N > 1000000000000){
return 0;
}
S = M % N;
cout << S << endl;
return 0;
}
I2luY2x1ZGU8aW9zdHJlYW0+CnVzaW5nIG5hbWVzcGFjZSBzdGQ7CgppbnQgbWFpbigpIHsKICAgIGxvbmcgbG9uZyBOLCBNLCBTOwogICAgCiAgICBjaW4gPj4gTSA+PiBOOwogICAgCiAgICBpZiAoTSA8IDAgfHwgTSA+IDEwMDAwMDAwMDAwMDApewogICAgICAgICAgIHJldHVybiAwOwogICAgfQogICAgCiAgICBlbHNlIGlmIChOIDwgMSB8fCBOID4gMTAwMDAwMDAwMDAwMCl7CiAgICAgICAgcmV0dXJuIDA7CiAgICB9CiAgICAKICAgIFMgPSBNICUgTjsKICAgIAogICAgY291dCA8PCBTIDw8IGVuZGw7CgogICAgcmV0dXJuIDA7Cn0K