function Main(_input) {
    var input = _input.split(" ");
    var num_A = parseInt(input[0]);
    var num_B = parseInt(input[1]);
    var num_N = parseInt(input[2]);
    var num_Manum_NVal = num_A <= num_B? num_A - 1 : num_B - 1;
    if( num_Manum_NVal < num_N) console.log(num_Manum_NVal);
    else{
        if((Math.floor(num_A * num_N / num_B) - num_A * Math.floor( num_N / num_B )) >= (Math.floor(num_A * 1 / num_B) - num_A * Math.floor( 1 / num_B ))){
            console.log(Math.floor(num_A * num_N / num_B) - num_A * Math.floor( num_N / num_B ));
        } else {
            console.log(Math.floor(num_A * 1 / num_B) - num_A * Math.floor( 1 / num_B ));
        }
    }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));