brainfuck-esotope, 269 bytes

Result

AC

Duration

764ms

Code [DL]

+[,.------------------------------------------------------------------------------------]+[>++++++++++++++++++++++++++++++++++++++++++++++++++[>,+<<[>>->+<<<-]>>.---------------------------------------------------------------------------[>[<<<+>>>-]<[+]]>[-]<<-]>,+.<<]

Disassembly

p[0] = 1;
while (p[0]) {
	p[0] = GETC();
	PUTC(p[0]);
	p[0] -= 84;
}
p[0] = 1;
p[1] = 0;
p[2] = 0;
p[3] = 0;
while (p[0]) {
	p[1] += 50;
	while (p[1]) {
		p[2] = GETC();
		p[2] -= p[0]-1;
		p[3] += p[0];
		p[0] = 0;
		PUTC(p[2]);
		p[2] -= 75;
		if (p[2]) {
			p[0] += p[3];
			p[3] = 0;
			p[2] = 0;
		}
		p[2] = 0;
		p[3] = 0;
		--p[1];
	}
	p[2] = GETC();
	++p[2];
	PUTC(p[2]);
}

stdin

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            K                                     

stdout

                 T                                
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            K!!!!!

stderr

strace