1. 字符串判定-最后一个有效字符

const readline = require('readline');
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

rl.on('line', (stringS) => {
    rl.on('line', (stringL) => {
        let indexS = 0;
        let indexL = 0;
        while(indexS < stringS.length && indexL < stringL.length) {
            if (stringS.charAt(indexS) === stringL.charAt(indexL)) {
                indexS++;
            }
            indexL++;
        }
        if (indexS === stringS.length) {
            console.log(indexL - 1);
        } else {
            console.log(-1);
        }
        rl.close();
    })
})