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