var main = (standardInput) => {
	var array = standardInput.split(' ');
  	var a = Number.parseInt(array[0]);
  	var b = Number.parseInt(array[1]);
	var c = Number.parseInt(array[2]);
  	if(a >= b+c){
    	console.log(0);
    }else{
		console.log(a-b-c);
    }
}

main(require('fs').readFileSync('/dev/stdin', 'UTF-8'));