fs = require('fs').readFileSync('/dev/stdin','utf-8');
tmp = fs.split(' ');
if(parseInt(tmp[0],10) == 0 || parseFloat(tmp[1]) == 0) { console.log(0); return; }
A = BigInt(parseInt(tmp[0],10));
B = BigInt(Math.floor(parseFloat(tmp[1]) * 100));
C = (A * B / BigInt(100)) + '';
if(C.indexOf('.') != -1) {
  C = C.substing(0,C.indexOf('.'));
}
console.log(C);
