
function main(input) {
  const inArray = input.trim().split(/\s|\n/);
  console.log(Array.from(inArray[2]).map((s, i) => {
    return (i+1) === parseInt(inArray[1]) ? s.toLowerCase() : s;
  }).join(''))
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));
