Mars Exploration 1

mars1.js

function main() {
    let N = readLine()
    let S = N.match(/.{1,3}/g);
    let R = 'SOS'.repeat(N.length / 3).match(/.{1,3}/g);
        
    let count = 0;
    
    for (let i in S) {
        for (let j in S[i]) {
         if (S[i][j] !== R[i][j]) {
             count++;
         }   
        }
    }
    
    console.log(count);
}