func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = 3e5 + 5;   int n, m;   int first[maxn], second[maxn];   void solve() {     cin >> n >> m;     for (int i = 1; i <= m; ++i) cin >> first[i] >> second[i];     int a, b;     a = first[1];     b = -1;     for (int i = 1; i <= m; ++i) {       if (first[i] != a && second[i] != a) {         if (first[i] != b && second[i] != b) {           if (b == -1)             b = first[i];           else             break;         }       }       if (i == m) {         puts( YES );         return;       }     }     a = -1;     b = second[1];     for (int i = 1; i <= m; ++i) {       if (first[i] != b && second[i] != b) {         if (first[i] != a && second[i] != a) {           if (a == -1)             a = first[i];           else             break;         }       }       if (i == m) {         puts( YES );         return;       }     }     a = -1;     b = second[1];     for (int i = 1; i <= m; ++i) {       if (first[i] != b && second[i] != b) {         if (first[i] != a && second[i] != a) {           if (a == -1)             a = second[i];           else             break;         }       }       if (i == m) {         puts( YES );         return;       }     }     a = first[1];     b = -1;     for (int i = 1; i <= m; ++i) {       if (first[i] != a && second[i] != a) {         if (first[i] != b && second[i] != b) {           if (b == -1)             b = second[i];           else             break;         }       }       if (i == m) {         puts( YES );         return;       }     }     puts( NO );   }   int main() { solve(); }   