unittest
{
	assert( [ "cupofcoffee", "cupofhottea" ].solve == 4 );
	assert( [ "abcde", "bcdea" ].solve == 5 );
	assert( [ "apple", "apple" ].solve == 0 );
}



import std.conv;
import std.range;
import std.stdio;

void main()
{
	stdin.byLineCopy.solve.writeln;
}

auto solve( Range )( Range input )
if( isInputRange!Range && is( ElementType!Range == string ) )
{
	auto s = input.front.to!( dchar[] );
	input.popFront;
	auto t = input.front.to!( dchar[] );
	
	auto ans = 0L;
	foreach( sc, tc; lockstep( s, t ) )
	{
		ans += ( sc != tc );
	}
	return ans;
}
