c++ primer 1.44 if 语句 例题 不解

#include <iostream>

int main() { // currVal is the number we're counting; we'll read new values into val

int currVal = 0, val = 0; // read first number and ensure that we have data to process if (std::cin >> currVal) { int cnt = 1; // store the count for the current value we're processing while (std::cin >> val) { // read the remaining numbers if (val == currVal) // if the values are the same ++cnt; // add 1 to cnt else { // otherwise, print the count for the previous value std::cout << currVal << " occurs " << cnt << " times" << std::endl; currVal = val; // remember the new value cnt = 1; // reset the counter } } // while loop ends here // remember to print the count for the last value in the file std::cout << currVal << " occurs " << cnt << " times" << std::endl; } // outermost if statement ends here return 0; 

}

源码如上 为何自己运行时最后一个数无法输出啊？