solution

sol

function fk(n) {
	return (n*(n + 1)) / 2;
}

var data = readline().split(' ').map(function(x) { return parseInt(x); });
var n = data[0];
var m = data[1];
var k = data[2];

var nL = k - 1;
var nR = n - k;

var max = 1;
var i = 1;
var j = m;
while(i < j) {
	var kk = Math.ceil((j + i) / 2);
	if(kk == max) {
		break;
	}
	var sR = 0;
	var sL = 0;

	if(nR > 0) {
		if(kk < nR) {
			sR = fk(kk - 1) + (nR - kk);
		} else {
			sR = fk(kk - 1) - fk(kk - 1 - nR);
		}
	}

	if(nL > 0) {
		if(kk < nL) {
			sL = fk(kk - 1) + (nL - kk);
		} else {
			sL = fk(kk - 1) - fk(kk - 1 - nL);
		}
	}

	var s = kk + sR + sL;
	
	if(s <= m) {
		max = kk;
		i = kk;
	} else {
		j = kk;
	}
}
print(max);