A length-\(N\) bidirectional arrow string \((3\leq N\leq 100)\) always consists of one <, \((N-2)\) copies of =, and one >, concatenated in this order. Conversely, under the constraints \(3\leq N\leq 100\), such a string always satisfies the condition of being a bidirectional arrow string. Thus, it is sufficient to check if the given string is of this type. Specifically, check if

• the first character is <,
• the \(N\)-th character is >, and
• the \(i\)-th character is = for all \(2\leq i\leq N-1\).

If the answers to all of the questions are Yes, then the answer is Yes; otherwise, the answer is No.
This can be implemented with an if statement and a for statement.

Sample code in C++:

#include <bits/stdc++.h>

using namespace std;

int main() {
	string s;
	cin>>s;
	int n=s.size();
	if(s[0]!='<'){
		cout<<"No"<<endl;
		return 0;
	}
	if(s[n-1]!='>'){
		cout<<"No"<<endl;
		return 0;
	}
	for(int i=1;i<n-1;i++){
		if(s[i]!='='){
			cout<<"No"<<endl;
			return 0;
		}
	}
	cout<<"Yes"<<endl;
	return 0;
}

Sample code in Python:

s=input()
flag=True
if s[0]!='<':
    flag=False
if s[-1]!='>':
    flag=False
for i in range(1,len(s)-1):
    if s[i]!='=':
        flag=False
if flag:
    print("Yes")
else:
    print("No")