string convert(string s, int n) {

// Edge case

if(n == 1) return s;

// Other cases

// Take string to store answer

string ans = "";

// We are going to traverse each row

for(int row = 0; row < n ; row++){

// for each row the next chracter is at index 2 * (n -1)

int increment = 2 * (n -1);

// For first and last rows

for(int i = row; i < s.length(); i+= increment){

ans += s[i];

// For middle rows there will be extra characters

if(row > 0 && row < n-1 && i+increment - 2 * row < s.length()){

ans += s[i+increment - 2 * row];

}

}

}

return ans;

}