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dfs.cpp

#include <cstdio>
#include <string>

int n = 4;
int k = 15;
int a[] = {1, 2, 4, 7};

bool dfs(int i, int sum)
{
  printf("i == %d, sum == %d\n", i, sum);
  if( i == n ) return sum == k;
  if( dfs(i+1, sum) ) return true;
  if( dfs(i+1, sum+a[i]) ) return true;

  return false;
}

void solve()
{
  if( dfs(0, 0) ) printf("Yes\n");
  else { printf("No\n"); }
}
 
int main(int argc, char *argv[])
{
  solve();
  
  return 0;
}