Evaluation of 1 st operator
if ( k == 1 ) { if ( operators [ k - 1 ] == ' + ' ) ans += stol ( operands [ k - 1 ] ) + stol ( operands [ k ] ) ; if ( operators [ k - 1 ] == ' - ' ) ans += stol ( operands [ k - 1 ] ) - stol ( operands [ k ] ) ; }