49841310.less

@font-size-min: 16px;
@font-size-max: 18px;
@font-size-diff: (@font-size-max - @font-size-min);

body {
    .eval(@font-size-diff);
    font-size: calc((100vw - @font-size-min) / @eval-result);
}

.eval(@expr) {
    @eval-result: @expr;  
}